Publications by authors named "Brendan H Lee"

73 Publications

Heterozygous variants in SPTBN1 cause intellectual disability and autism.

Am J Med Genet A 2021 Apr 13. Epub 2021 Apr 13.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

Spectrins are common components of cytoskeletons, binding to cytoskeletal elements and the plasma membrane, allowing proper localization of essential membrane proteins, signal transduction, and cellular scaffolding. Spectrins are assembled from α and β subunits, encoded by SPTA1 and SPTAN1 (α) and SPTB, SPTBN1, SPTBN2, SPTBN4, and SPTBN5 (β). Pathogenic variants in various spectrin genes are associated with erythroid cell disorders (SPTA1, SPTB) and neurologic disorders (SPTAN1, SPTBN2, and SPTBN4), but no phenotypes have been definitively associated with variants in SPTBN1 or SPTBN5. Through exome sequencing and case matching, we identified seven unrelated individuals with heterozygous SPTBN1 variants: two with de novo missense variants and five with predicted loss-of-function variants (found to be de novo in two, while one was inherited from a mother with a history of learning disabilities). Common features include global developmental delays, intellectual disability, and behavioral disturbances. Autistic features (4/6) and epilepsy (2/7) or abnormal electroencephalogram without overt seizures (1/7) were present in a subset. Identification of loss-of-function variants suggests a haploinsufficiency mechanism, but additional functional studies are required to fully elucidate disease pathogenesis. Our findings support the essential roles of SPTBN1 in human neurodevelopment and expand the knowledge of human spectrinopathy disorders.
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http://dx.doi.org/10.1002/ajmg.a.62201DOI Listing
April 2021

Pregnancy in women with osteogenesis imperfecta: Pregnancy characteristics, maternal, and neonatal outcomes.

Am J Obstet Gynecol MFM 2021 Mar 26:100362. Epub 2021 Mar 26.

Departments of Obstetrics and Gynecology, David Geffen School of Medicine at University of California at Los Angeles (UCLA) Los Angeles, California; Departments of Human Genetics, David Geffen School of Medicine at University of California at Los Angeles (UCLA) Los Angeles, California; Departments of Orthopaedic Surgery, David Geffen School of Medicine at University of California at Los Angeles (UCLA) Los Angeles, California; Departments of Pediatrics, David Geffen School of Medicine at University of California at Los Angeles (UCLA) Los Angeles, California. Electronic address:

Background: Women with rare diseases such as osteogenesis imperfecta may consider pregnancy, although data regarding outcomes, specific risks, and management strategies is lacking.

Objective: The Brittle Bone Disorders Consortium of the National Institute of Health Rare Diseases Clinical Research Network established an Osteogenesis Imperfecta Pregnancy Registry to collect and evaluate pregnancy, maternal, and neonatal outcomes in women with osteogenesis imperfecta STUDY DESIGN: This is a cross-sectional, survey-based study. Appropriate participants of the Brittle Bone Disorders Consortium Contact Registry were invited to participate in the study. Self-reported information regarding pregnancy characteristics and maternal and neonatal outcomes was compared to the general population, referenced by literature-based standards, and comparisons between cohorts of women and fetuses with osteogenesis imperfecta were evaluated to determine if the presence of osteogenesis imperfecta conveyed an increase in antepartum, intrapartum, and postpartum complications and an increase in adverse neonatal outcomes when compared to the general population.

Results: 132 Participants completed the survey. Compared to the general population, women with osteogenesis imperfecta had higher rates of diabetes in pregnancy (13.3% vs. 7%, p=0.049, CI: 7.0%-19.6%), cesarean section (68.5% vs. 32.7%, p<0.001, CI: 59.9-77.1%), need for blood transfusion (8.3% vs. 1.5%, p=0.019, CI: 3.9-12.8%), and antepartum and postpartum fractures (RR 221, 95% CI: 59.3-823, p<0.001). Maternal hospitalization and cesarean rates were higher in individuals with moderate or severe osteogenesis imperfecta as compared to the women who reported mild osteogenesis imperfecta. Neonates born to women with osteogenesis imperfecta had higher risk for being low (26.2% vs. 6.8%, p<0.001) or very low birth weight (13.8% vs. 1.4%, p<0.001) infants as compared to the general population. Neonates born to women with osteogenesis imperfecta had a higher rate of neonatal intensive care unit admissions (19% vs. 5.68%, p<0.001) and higher neonatal mortality at 28 days of life (4.8% vs. 0.4%, p=0.026), regardless of neonatal osteogenesis imperfecta status.

Conclusion: Pregnancies for women with osteogenesis imperfecta are at an increased risk for complications including hemorrhage, fractures, diabetes, and increased neonatal morbidity.
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http://dx.doi.org/10.1016/j.ajogmf.2021.100362DOI Listing
March 2021

regulates the action of nitrogen-containing bisphosphonates on bone.

Sci Transl Med 2020 05;12(544)

Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital and Harvard School of Dental Medicine, Boston, MA 02114, USA.

Nitrogen-containing bisphosphonates (N-BPs), such as alendronate, are the most widely prescribed medications for diseases involving bone, with nearly 200 million prescriptions written annually. Recently, widespread use of N-BPs has been challenged due to the risk of rare but traumatic side effects such as atypical femoral fracture (AFF) and osteonecrosis of the jaw (ONJ). N-BPs bind to and inhibit farnesyl diphosphate synthase, resulting in defects in protein prenylation. Yet, it remains poorly understood what other cellular factors might allow N-BPs to exert their pharmacological effects. Here, we performed genome-wide studies in cells and patients to identify the poorly characterized gene, Loss of function results in selective resistance to N-BP-mediated loss of cell viability and the prevention of alendronate-mediated inhibition of prenylation. is required for alendronate inhibition of osteoclast function, and -deficient mice have impaired therapeutic responses to alendronate in both postmenopausal and senile (old age) osteoporosis models. Last, we performed exome sequencing on patients taking N-BPs that suffered ONJ or an AFF. is one of three genes that contain rare nonsynonymous coding variants in patients with ONJ or an AFF that is also differentially expressed in poor outcome groups of patients treated with N-BPs. We functionally validated this patient variation in as conferring cellular hypersensitivity to N-BPs. Our work adds key insight into the mechanistic action of N-BPs and the processes that might underlie differential responsiveness to N-BPs in people.
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http://dx.doi.org/10.1126/scitranslmed.aav9166DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7882121PMC
May 2020

Further delineation of the clinical spectrum of KAT6B disorders and allelic series of pathogenic variants.

Genet Med 2020 08 19;22(8):1338-1347. Epub 2020 May 19.

Division of Genetics and Genomics, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.

Purpose: Genitopatellar syndrome and Say-Barber-Biesecker-Young-Simpson syndrome are caused by variants in the KAT6B gene and are part of a broad clinical spectrum called KAT6B disorders, whose variable expressivity is increasingly being recognized.

Methods: We herein present the phenotypes of 32 previously unreported individuals with a molecularly confirmed diagnosis of a KAT6B disorder, report 24 new pathogenic KAT6B variants, and review phenotypic information available on all published individuals with this condition. We also suggest a classification of clinical subtypes within the KAT6B disorder spectrum.

Results: We demonstrate that cerebral anomalies, optic nerve hypoplasia, neurobehavioral difficulties, and distal limb anomalies other than long thumbs and great toes, such as polydactyly, are more frequently observed than initially reported. Intestinal malrotation and its serious consequences can be present in affected individuals. Additionally, we identified four children with Pierre Robin sequence, four individuals who had increased nuchal translucency/cystic hygroma prenatally, and two fetuses with severe renal anomalies leading to renal failure. We also report an individual in which a pathogenic variant was inherited from a mildly affected parent.

Conclusion: Our work provides a comprehensive review and expansion of the genotypic and phenotypic spectrum of KAT6B disorders that will assist clinicians in the assessment, counseling, and management of affected individuals.
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http://dx.doi.org/10.1038/s41436-020-0811-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7737399PMC
August 2020

Exome sequencing compared with standard genetic tests for critically ill infants with suspected genetic conditions.

Genet Med 2020 08 27;22(8):1303-1310. Epub 2020 Apr 27.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Purpose: As exome sequencing (ES) is increasingly used as a diagnostic tool, we aimed to compare ES with status quo genetic diagnostic workup for infants with suspected genetic disorders in terms of identifying diagnoses, survival, and cost of care.

Methods: We studied newborns and infants admitted to intensive care with a suspected genetic etiology within the first year of life at a US quaternary-referral children's hospital over 5 years. In this propensity-matched cohort study using electronic medical record data, we compared patients who received ES as part of a diagnostic workup (ES cohort, n = 368) with clinically similar patients who did not receive ES (No-ES cohort, n = 368).

Results: Diagnostic yield (27.4% ES, 25.8% No-ES; p = 0.62) and 1-year survival (80.2% ES, 84.8% No-ES; p = 0.10) were no different between cohorts. ES cohort patients had higher cost of admission, diagnostic investigation, and genetic testing (all p < 0.01).

Conclusion: ES did not differ from status quo genetic testing collectively in terms of diagnostic yield or patient survival; however, it had high yield as a single test, led to complementary classes of diagnoses, and was associated with higher costs. Further work is needed to define the most efficient use of diagnostic ES for critically ill newborns and infants.
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http://dx.doi.org/10.1038/s41436-020-0798-1DOI Listing
August 2020

De novo EIF2AK1 and EIF2AK2 Variants Are Associated with Developmental Delay, Leukoencephalopathy, and Neurologic Decompensation.

Am J Hum Genet 2020 04 19;106(4):570-583. Epub 2020 Mar 19.

Stanford Center for Undiagnosed Diseases, Stanford University, Stanford, CA 94305, USA; Department of Pediatrics, Stanford University School of Medicine, Stanford, CA 94305, USA.

EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.
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http://dx.doi.org/10.1016/j.ajhg.2020.02.016DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118694PMC
April 2020

Notch Signaling in Skeletal Development, Homeostasis and Pathogenesis.

Biomolecules 2020 02 19;10(2). Epub 2020 Feb 19.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.

Skeletal development is a complex process which requires the tight regulation of gene activation and suppression in response to local signaling pathways. Among these pathways, Notch signaling is implicated in governing cell fate determination, proliferation, differentiation and apoptosis of skeletal cells-osteoblasts, osteoclasts, osteocytes and chondrocytes. Moreover, human genetic mutations in Notch components emphasize the critical roles of Notch signaling in skeletal development and homeostasis. In this review, we focus on the physiological roles of Notch signaling in skeletogenesis, postnatal bone and cartilage homeostasis and fracture repair. We also discuss the pathological gain- and loss-of-function of Notch signaling in bone and cartilage, resulting in osteosarcoma and age-related degenerative diseases, such as osteoporosis and osteoarthritis. Understanding the physiological and pathological function of Notch signaling in skeletal tissues using animal models and human genetics will provide new insights into disease pathogenesis and offer novel approaches for the treatment of bone/cartilage diseases.
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http://dx.doi.org/10.3390/biom10020332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7072615PMC
February 2020

Hearing loss in individuals with osteogenesis imperfecta in North America: Results from a multicenter study.

Am J Med Genet A 2020 04 26;182(4):697-704. Epub 2019 Dec 26.

Department of Pediatric Orthopedic Surgery, Hospital for Special Surgery, New York, New York.

Hearing loss (HL) is an extra-skeletal manifestation of the connective tissue disorder osteogenesis imperfecta (OI). Systematic evaluation of the prevalence and characteristics of HL in COL1A1/COL1A2-related OI will contribute to a better clinical management of individuals with OI. We collected and analyzed pure-tone audiometry data from 312 individuals with OI who were enrolled in the Linked Clinical Research Centers and the Brittle Bone Disorders Consortium. The prevalence, type, and severity of HL in COL1A1/COL1A2-related OI are reported. We show that the prevalence of HL in OI is 28% and increased with age in Type I OI but not in Types III and IV. Individuals with OI Types III and IV are at a higher risk to develop HL in the first decade of life when compared to OI Type I. We also show that the prevalence of SNHL is higher in females with OI compared to males. This study reveals new insights regarding prevalence of HL in OI including a lower general prevalence of HL in COL1A1/COL1A2-related OI than previously reported (28.3 vs. 65%) and high prevalence of SNHL in females. Our data support the need in early routine hearing evaluation in all types of OI that can be adjusted to the severity of the skeletal disease.
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http://dx.doi.org/10.1002/ajmg.a.61464DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7385724PMC
April 2020

Mutations in ANAPC1, Encoding a Scaffold Subunit of the Anaphase-Promoting Complex, Cause Rothmund-Thomson Syndrome Type 1.

Am J Hum Genet 2019 09 11;105(3):625-630. Epub 2019 Jul 11.

Centre Hospitalier Universitaire Sainte-Justine Research Center, University of Montreal, Montreal, QC H3T 1C5, Canada; Department of Pediatrics, University of Montreal, Montreal, QC H3T 1C5, Canada. Electronic address:

Rothmund-Thomson syndrome (RTS) is an autosomal-recessive disorder characterized by poikiloderma, sparse hair, short stature, and skeletal anomalies. Type 2 RTS, which is defined by the presence of bi-allelic mutations in RECQL4, is characterized by increased cancer susceptibility and skeletal anomalies, whereas the genetic basis of RTS type 1, which is associated with juvenile cataracts, is unknown. We studied ten individuals, from seven families, who had RTS type 1 and identified a deep intronic splicing mutation of the ANAPC1 gene, a component of the anaphase-promoting complex/cyclosome (APC/C), in all affected individuals, either in the homozygous state or in trans with another mutation. Fibroblast studies showed that the intronic mutation causes the activation of a 95 bp pseudoexon, leading to mRNAs with premature termination codons and nonsense-mediated decay, decreased ANAPC1 protein levels, and prolongation of interphase. Interestingly, mice that were heterozygous for a knockout mutation have an increased incidence of cataracts. Our results demonstrate that deficiency in the APC/C is a cause of RTS type 1 and suggest a possible link between the APC/C and RECQL4 helicase because both proteins are involved in DNA repair and replication.
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http://dx.doi.org/10.1016/j.ajhg.2019.06.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731352PMC
September 2019

Using the Delphi method to identify clinicians' perceived importance of pediatric exome sequencing results.

Genet Med 2020 01 5;22(1):69-76. Epub 2019 Jul 5.

Baylor College of Medicine, Center for Medical Ethics and Health Policy, Houston, TX, USA.

Purpose: Information obtained from clinical exome sequencing (ES) may impact clinical care or other aspects of a patient's life. Little is known about clinicians' perceptions regarding either the value of ES results or which among various outcomes are most relevant to determine value. This study aims to assess clinicians' opinions of the importance of ES results for medical decision making and identify a set of outcomes to be measured in future ES evaluations.

Methods: Expert opinion regarding the value of remarkable (diagnostic/positive) and unremarkable (nondiagnostic/negative) ES results was elicited via the Delphi method, consisting of two survey rounds and a teleconference. Participants had expertise in caring for clinically diverse infants and children with suspected underlying genetic etiologies. Descriptive statistics and (dis)agreement were calculated for each survey item.

Results: Remarkable ES results were considered important for 17 outcome domains. Unremarkable ES results were also perceived as important in terms of psychological impact and ability to inform follow-up diagnostic test decisions.

Conclusion: Clinicians regard remarkable ES results as more important in many ways than findings from other diagnostic modalities. Unremarkable ES results were not considered unimportant for decision making, but rather uncertain in most outcome domains.
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http://dx.doi.org/10.1038/s41436-019-0601-3DOI Listing
January 2020

Bmi1 Suppresses Adipogenesis in the Hematopoietic Stem Cell Niche.

Stem Cell Reports 2019 09 27;13(3):545-558. Epub 2019 Jun 27.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address:

Bone marrow stromal cells (BMSCs) that express high levels of stem cell factor (SCF) and CXC chemokine ligand 12 (CXCL12) are one crucial component of the hematopoietic stem cell (HSC) niche. While the secreted factors produced by BMSCs to support HSCs have been well described, little is known regarding the transcriptional regulators controlling the cell fate of BMSCs and thus indirectly maintaining HSCs. BMI1 is a polycomb group protein that regulates HSCs both cell intrinsically and extrinsically, but it is unknown in which cell type and how BMI1 functions to maintain HSCs extrinsically. Here we show that Bmi1 maintains HSCs by preventing adipogenic differentiation of BMSCs. Bmi1 is highly expressed in BMSCs but becomes downregulated upon adipogenic differentiation and during aging. Deleting Bmi1 from BMSCs increased marrow adipocytes, induced HSC quiescence and depletion, and impaired hematopoiesis. We found that BMI1 repressed multiple developmental programs in BMSCs by safeguarding the repressive epigenetic marks histone H2A ubiquitylation and H3 lysine 27 trimethylation. We identified a novel adipogenic program governed by Pax3, which BMI1 repressed in BMSCs. Our results establish Bmi1 as a critical regulator of BMSC cell fate that suppresses marrow adipogenesis to create a supportive niche for HSCs.
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http://dx.doi.org/10.1016/j.stemcr.2019.05.027DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6739622PMC
September 2019

Effects of Aspirin on Growth Factor Release From Freshly Isolated Leukocyte-Rich Platelet-Rich Plasma in Healthy Men: A Prospective Fixed-Sequence Controlled Laboratory Study.

Am J Sports Med 2019 04 19;47(5):1223-1229. Epub 2019 Mar 19.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

Background: The benefits of platelet-rich plasma (PRP) are believed to be in part dependent on growth factor release after platelet activation. Platelet activation is complex and involves multiple mechanisms. One important mechanism is driven by cyclooxygenase 1 (COX-1)-mediated conversion of arachidonic acid (AA) to precursor prostaglandins that then mediate proinflammatory responses that trigger growth factor release. Acetylsalicylic acid (ASA; also known as aspirin) is known to irreversibly inhibit COX-1, thereby blocking AA-mediated signaling; however, it is unclear whether ASA use alters growth factor release from freshly isolated PRP.

Purpose: To assess the effects of low-dose ASA use on activation of growth factor release from freshly isolated human PRP via AA and thrombin (TBN).

Study Design: Controlled laboratory study.

Methods: Twelve healthy men underwent blood collection and leukocyte-rich PRP (LR-PRP) preparation through a double-spin protocol to obtain baseline whole blood and PRP counts the same day. PRP was aliquoted into 3 groups: nonactivated, AA activated, and TBN activated. Immediately after activation, the concentrations of transforming growth factor β1 (TGF-β1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor AB (PDGF-AB) were measured using enzyme-linked immunosorbent assays (ELISAs). The same 12 participants were then placed on an 81-mg daily dose of oral ASA for 14 days. Repeat characterization of whole blood and PRP analyses was done on day 14, followed by repeat ELISAs of growth factors under the same nonactivated and activated settings as previously stated.

Results: Fourteen days of daily ASA had no effect on the number of platelets and leukocytes measured in whole blood and LR-PRP. Compared with nonactivated LR-PRP, AA- and TBN-mediated activation led to significant release of VEGF and PDGF-AB. In contrast, release of TGF-β1 from LR-PRP was observed only with activation by AA, not with TBN. Consistent with its inhibitory role in AA signaling, ASA significantly inhibited AA-mediated release of all 3 growth factors measured in this study. Although ASA had no effect on TBN-mediated release of VEGF and TGF-β1 from LR-PRP, ASA did partially block TBN-mediated release of PDGF-AB, although the mechanism remains unclear.

Conclusion: Daily use of low-dose ASA reduces VEGF, PDGF-AB, and TGF-β1 expression in freshly isolated human LR-PRP when activated with AA.

Clinical Relevance: Reduction in growth factor release attributed to daily use of low-dose ASA or other COX inhibitors can be mitigated when PRP samples are activated with TBN. Clinical studies are needed to determine whether activation before PRP injection is needed in all applications where ASA is in use and to what extent ASA may inhibit growth factor release in vivo at the site of injury.
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http://dx.doi.org/10.1177/0363546519827294DOI Listing
April 2019

Untargeted metabolomic profiling reveals multiple pathway perturbations and new clinical biomarkers in urea cycle disorders.

Genet Med 2019 09 23;21(9):1977-1986. Epub 2019 Jan 23.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Purpose: Untargeted metabolomic analysis is increasingly being used in the screening and management of individuals with inborn errors of metabolism (IEM). We aimed to test whether untargeted metabolomic analysis in plasma might be useful for monitoring the disease course and management of urea cycle disorders (UCDs).

Methods: Untargeted mass spectrometry-based metabolomic analysis was used to generate z-scores for more than 900 metabolites in plasma from 48 individuals with various UCDs. Pathway analysis was used to identify common pathways that were perturbed in each UCD.

Results: Our metabolomic analysis in plasma identified multiple potentially neurotoxic metabolites of arginine in arginase deficiency and, thus, may have utility in monitoring the efficacy of treatment in arginase deficiency. In addition, we were also able to detect multiple biochemical perturbations in all UCDs that likely reflect clinical management, including metabolite alterations secondary to dietary and medication management.

Conclusion: In addition to utility in screening for IEM, our results suggest that untargeted metabolomic analysis in plasma may be beneficial for monitoring efficacy of clinical management and off-target effects of medications in UCDs and potentially other IEM.
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http://dx.doi.org/10.1038/s41436-019-0442-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6650380PMC
September 2019

Expanding the Spectrum of BAF-Related Disorders: De Novo Variants in SMARCC2 Cause a Syndrome with Intellectual Disability and Developmental Delay.

Am J Hum Genet 2019 01 20;104(1):164-178. Epub 2018 Dec 20.

Department of Clinical Genetics, Erasmus Medical Center, 3015 GD Rotterdam, the Netherlands.

SMARCC2 (BAF170) is one of the invariable core subunits of the ATP-dependent chromatin remodeling BAF (BRG1-associated factor) complex and plays a crucial role in embryogenesis and corticogenesis. Pathogenic variants in genes encoding other components of the BAF complex have been associated with intellectual disability syndromes. Despite its significant biological role, variants in SMARCC2 have not been directly associated with human disease previously. Using whole-exome sequencing and a web-based gene-matching program, we identified 15 individuals with variable degrees of neurodevelopmental delay and growth retardation harboring one of 13 heterozygous variants in SMARCC2, most of them novel and proven de novo. The clinical presentation overlaps with intellectual disability syndromes associated with other BAF subunits, such as Coffin-Siris and Nicolaides-Baraitser syndromes and includes prominent speech impairment, hypotonia, feeding difficulties, behavioral abnormalities, and dysmorphic features such as hypertrichosis, thick eyebrows, thin upper lip vermilion, and upturned nose. Nine out of the fifteen individuals harbor variants in the highly conserved SMARCC2 DNA-interacting domains (SANT and SWIRM) and present with a more severe phenotype. Two of these individuals present cardiac abnormalities. Transcriptomic analysis of fibroblasts from affected individuals highlights a group of differentially expressed genes with possible roles in regulation of neuronal development and function, namely H19, SCRG1, RELN, and CACNB4. Our findings suggest a novel SMARCC2-related syndrome that overlaps with neurodevelopmental disorders associated with variants in BAF-complex subunits.
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http://dx.doi.org/10.1016/j.ajhg.2018.11.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6323608PMC
January 2019

Recurrent mosaic MTOR c.5930C > T (p.Thr1977Ile) variant causing megalencephaly, asymmetric polymicrogyria, and cutaneous pigmentary mosaicism: Case report and review of the literature.

Am J Med Genet A 2019 03 19;179(3):475-479. Epub 2018 Dec 19.

Department of Pediatrics, Section of Neurology and Developmental Neuroscience, Baylor College of Medicine, Houston, Texas.

Genetic alterations leading to overactivation of mammalian target of rapamycin (mTOR) signaling result in brain overgrowth syndromes such as focal cortical dysplasia (FCD) and megalencephaly. Megalencephaly with cutis tri-color of the Blaschko-linear type pigmentary mosaicism and intellectual disability is a rare neurodevelopmental disorder attributed to the recurrent mosaic c.5930C > T (p.Thr1977Ile) MTOR variant. This variant was previously reported at low to intermediate levels of mosaicism in the peripheral blood of three unrelated individuals with consistent clinical findings. We report a fourth case of a 3-year-old female presenting with megalencephaly, obstructive hydrocephalus due to cerebral aqueductal stenosis, asymmetric polymicrogyria, dysgenesis of the corpus callosum, hypotonia, developmental delay, and cutaneous pigmentary mosaicism. Oligonucleotide and SNP chromosomal microarray (CMA), karyotype, and trio whole exome sequencing (WES) in the peripheral blood, as well as a targeted gene variant panel from fibroblasts derived from hyperpigmented and non-hyperpigmented skin did not detect any abnormalities in MTOR or other genes associated with brain overgrowth syndromes. Unlike the previously reported cases, the de novo c.5930C > T (p.Thr1977Ile) MTOR variant was detected at 32% mosaicism in our patient only after WES was performed on fibroblast-derived DNA from the hyperpigmented skin. This case demonstrates the tissue variability in mosaic expression of the recurrent p.Thr1977Ile MTOR variant, emphasizes the need for skin biopsies in the genetic evaluation of patients with skin pigmentary mosaicism, and expands the clinical phenotype associated with this pathogenic MTOR variant.
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http://dx.doi.org/10.1002/ajmg.a.61007DOI Listing
March 2019

Effect of Genetic Diagnosis on Patients with Previously Undiagnosed Disease.

N Engl J Med 2018 11 10;379(22):2131-2139. Epub 2018 Oct 10.

From Harvard Medical School (K.S., C.E., I.S.K., J.L., A.T.M., D.A.S.), Brigham and Women's Hospital (J.L.), and Massachusetts General Hospital (D.A.S.) - all in Boston; the National Institutes of Health Clinical Center (D.R.A., W.A.G., J.J.M., C.J.T.) and the National Human Genome Research Institute (A.L.W.), Bethesda, and the University of Maryland, College Park (A.M.C.-J., B.K., L.P.) - all in Maryland; Baylor College of Medicine, Houston (C.A.B., H.J.B., C.M.E., B.H.L., X.L., M.F.W., S.Y.); Stanford University, Stanford (J.A.B., C.R., M.T.W., E.A.A.), and the University of California, Los Angeles, Los Angeles (S.F.N., C.G.S.P.) - both in California; Vanderbilt University, Nashville (R.H., J.A.P.); HudsonAlpha Institute for Biotechnology, Huntsville, AL (H.J.J., E.A.W.); Oregon Health and Science University, Portland (D.M.K.); the Pacific Northwest National Laboratory, Richland, WA (T.O.M.); the University of Oregon, Eugene (J.H.P., M.W.); and Duke University, Durham, NC (V.S., N.M.W.).

Background: Many patients remain without a diagnosis despite extensive medical evaluation. The Undiagnosed Diseases Network (UDN) was established to apply a multidisciplinary model in the evaluation of the most challenging cases and to identify the biologic characteristics of newly discovered diseases. The UDN, which is funded by the National Institutes of Health, was formed in 2014 as a network of seven clinical sites, two sequencing cores, and a coordinating center. Later, a central biorepository, a metabolomics core, and a model organisms screening center were added.

Methods: We evaluated patients who were referred to the UDN over a period of 20 months. The patients were required to have an undiagnosed condition despite thorough evaluation by a health care provider. We determined the rate of diagnosis among patients who subsequently had a complete evaluation, and we observed the effect of diagnosis on medical care.

Results: A total of 1519 patients (53% female) were referred to the UDN, of whom 601 (40%) were accepted for evaluation. Of the accepted patients, 192 (32%) had previously undergone exome sequencing. Symptoms were neurologic in 40% of the applicants, musculoskeletal in 10%, immunologic in 7%, gastrointestinal in 7%, and rheumatologic in 6%. Of the 382 patients who had a complete evaluation, 132 received a diagnosis, yielding a rate of diagnosis of 35%. A total of 15 diagnoses (11%) were made by clinical review alone, and 98 (74%) were made by exome or genome sequencing. Of the diagnoses, 21% led to recommendations regarding changes in therapy, 37% led to changes in diagnostic testing, and 36% led to variant-specific genetic counseling. We defined 31 new syndromes.

Conclusions: The UDN established a diagnosis in 132 of the 382 patients who had a complete evaluation, yielding a rate of diagnosis of 35%. (Funded by the National Institutes of Health Common Fund.).
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http://dx.doi.org/10.1056/NEJMoa1714458DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6481166PMC
November 2018

Heterozygous WNT1 variant causing a variable bone phenotype.

Am J Med Genet A 2018 11 24;176(11):2419-2424. Epub 2018 Sep 24.

University of California, San Diego, La Jolla, California.

Osteogenesis imperfecta (OI) is a family of heritable disorders of bone fragility. Most individuals with OI have mutations in the genes encoding type I collagen; at least 17 other genes have been associated with OI. Biallelic loss-of-function mutations in WNT1 cause severe OI. Heterozygous missense variants in WNT1 are responsible for early-onset osteoporosis with variable bone phenotypes. Herein, we report a third-generation family with four affected individuals, some presenting with multiple low-impact fractures in childhood and others presenting with early-onset osteoporosis without a striking fracture history. A WNT1 variant (c. 1051 > C; p.Trp351Arg) was identified in the proband and segregated with a bone phenotype in three additional family members, consistent with autosomal dominant inheritance. In the proband, whole genome sequencing also revealed a de novo duplication (434 kb) of 22q11.2 that involves 25 genes, 4 of which are associated with human disease when haploinsufficient. Though smaller than the typical (1.5 Mb) 22q11.2 duplication, the duplication in the proband may be responsible for additional nonosseous aspects of his phenotype (hypotonia, developmental delay, small genitalia, strabismus, and depression in preadolescence). This case demonstrates the variability of bone phenotype conferred by a WNT1 variant and extends the spectrum of bone phenotypes associated with heterozygous WNT1 mutations.
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http://dx.doi.org/10.1002/ajmg.a.40347DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6289778PMC
November 2018

Argininosuccinate Lyase Deficiency Causes an Endothelial-Dependent Form of Hypertension.

Am J Hum Genet 2018 08;103(2):276-287

Program in Developmental Biology, Baylor College of Medicine, Houston, TX 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address:

Primary hypertension is a major risk factor for ischemic heart disease, stroke, and chronic kidney disease. Insights obtained from the study of rare Mendelian forms of hypertension have been invaluable in elucidating the mechanisms causing primary hypertension and development of antihypertensive therapies. Endothelial cells play a key role in the regulation of blood pressure; however, a Mendelian form of hypertension that is primarily due to endothelial dysfunction has not yet been described. Here, we show that the urea cycle disorder, argininosuccinate lyase deficiency (ASLD), can manifest as a Mendelian form of endothelial-dependent hypertension. Using data from a human clinical study, a mouse model with endothelial-specific deletion of argininosuccinate lyase (Asl), and in vitro studies in human aortic endothelial cells and induced pluripotent stem cell-derived endothelial cells from individuals with ASLD, we show that loss of ASL in endothelial cells leads to endothelial-dependent vascular dysfunction with reduced nitric oxide (NO) production, increased oxidative stress, and impaired angiogenesis. Our findings show that ASLD is a unique model for studying NO-dependent endothelial dysfunction in human hypertension.
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http://dx.doi.org/10.1016/j.ajhg.2018.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6080833PMC
August 2018

Combinatorial Prg4 and Il-1ra Gene Therapy Protects Against Hyperalgesia and Cartilage Degeneration in Post-Traumatic Osteoarthritis.

Hum Gene Ther 2019 02 17;30(2):225-235. Epub 2018 Oct 17.

1 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas.

Osteoarthritis (OA) is a degenerative disease of synovial joints characterized by progressive loss of articular cartilage, subchondral bone remodeling, and intra-articular inflammation with synovitis that results in chronic pain and motor impairment. Despite the economic and health impacts, current medical therapies are targeted at symptomatic relief of OA and fail to alter its progression. Given the complexity of OA pathogenesis, we hypothesized that a combinatorial gene therapy approach, designed to inhibit inflammation with interleukin-1 receptor antagonist (IL-1Ra) while promoting chondroprotection using lubricin (PRG4), would improve preservation of the joint compared to monotherapy alone. Employing two surgical techniques to model mild, moderate and severe posttraumatic OA, we found that combined delivery of helper-dependent adenoviruses (HDVs), expressing IL-1Ra and PRG4, preserved articular cartilage better than either monotherapy in both models as demonstrated by preservation of articular cartilage volume and surface area. This improved protection was associated with increased expression of proanabolic and cartilage matrix genes together with decreased expression of catabolic genes and inflammatory mediators. In addition to improvements in joint tissues, this combinatorial gene therapy prolonged protection against thermal hyperalgesia compared to either monotherapy. Taken together, our results show that a combinatorial strategy is superior to monotherapeutic approaches for treatment of posttraumatic OA.
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http://dx.doi.org/10.1089/hum.2018.106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383580PMC
February 2019

Atypical Alexander disease with dystonia, retinopathy, and a brain mass mimicking astrocytoma.

Neurol Genet 2018 Aug 20;4(4):e248. Epub 2018 Jul 20.

Department of Molecular and Human Genetics (K.M., L.C.B., M.J., R.A.L., M.X., J.A.R., R.C., C.M.E., Y.Y., B.H.L., P.M.M., S.U.D.), Department of Neurology (J.J., D.V., P.M.M), and Department of Ophthalmology (R.A.L.), Baylor College of Medicine; Department of Pathology (G.N.F.), Department of Neuro-Oncology (M.P.-P.), and Department of Diagnostic Imaging (M.K.G.-M.), The University of Texas MD Anderson Cancer Center; Michael E. DeBakey VA Medical Center (P.M.M.); Baylor Genetics (C.M.E., Y.Y.); and Department of Medicine (S.U.D.), Baylor College of Medicine, Houston, TX.

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http://dx.doi.org/10.1212/NXG.0000000000000248DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6055357PMC
August 2018

Disease-Modifying Osteoarthritis Treatment With Interleukin-1 Receptor Antagonist Gene Therapy in Small and Large Animal Models.

Arthritis Rheumatol 2018 11 10;70(11):1757-1768. Epub 2018 Sep 10.

Baylor College of Medicine, Houston, Texas, and GeneQuine Biotherapeutics GmbH, Hamburg, Germany.

Objective: Gene therapy holds great promise for the treatment of osteoarthritis (OA) because a single intraarticular injection can lead to long-term expression of therapeutic proteins within the joint. This study was undertaken to investigate the use of a helper-dependent adenovirus (HDAd)-mediated intraarticular gene therapy approach for long-term expression of interleukin-1 receptor antagonist (IL-1Ra) as sustained symptomatic and disease-modifying therapy for OA.

Methods: In mouse models of OA, efficacy of HDAd-IL-1Ra was evaluated by histologic analysis, micro-computed tomography (micro-CT), and hot plate analysis. In a horse OA model, safety and efficacy of HDAd-IL-1Ra were evaluated by blood chemistry, analyses of synovial fluid, synovial membrane, and cartilage, and gross pathology and lameness assessments.

Results: In skeletally immature mice, HDAd-IL-1Ra prevented development of cartilage damage, osteophytes, and synovitis. In skeletally immature and mature mice, treatment with HDAd-interleukin-1 receptor antagonist post-OA induction resulted in improved-albeit not significantly-cartilage status assessed histologically and significantly increased cartilage volume, cartilage surface, and bone surface covered by cartilage as assessed by micro-CT. Fewer osteophytes were observed in HDAd-IL-1Ra-treated skeletally immature mice. Synovitis was not affected in skeletally immature or mature mice. HDAd-IL-1Ra protected against disease-induced thermal hyperalgesia in skeletally mature mice. In the horse OA model, HDAd-IL-1Ra therapy significantly improved lameness parameters, indicating efficient symptomatic treatment. Moreover, macroscopically and histologically assessed cartilage and synovial membrane parameters were significantly improved, suggesting disease-modifying efficacy.

Conclusion: These data from OA models in small and large animals demonstrated safe symptomatic and disease-modifying treatment with an HDAd-expressing IL-1Ra. Furthermore, this study establishes HDAd as a vector for joint gene therapy.
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http://dx.doi.org/10.1002/art.40668DOI Listing
November 2018

De Novo Missense Variants in TRAF7 Cause Developmental Delay, Congenital Anomalies, and Dysmorphic Features.

Am J Hum Genet 2018 07 28;103(1):154-162. Epub 2018 Jun 28.

Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA; Baylor Genetics, Houston, TX 77021, USA.

TRAF7 is a multi-functional protein involved in diverse signaling pathways and cellular processes. The phenotypic consequence of germline TRAF7 variants remains unclear. Here we report missense variants in TRAF7 in seven unrelated individuals referred for clinical exome sequencing. The seven individuals share substantial phenotypic overlap, with developmental delay, congenital heart defects, limb and digital anomalies, and dysmorphic features emerging as key unifying features. The identified variants are de novo in six individuals and comprise four distinct missense changes, including a c.1964G>A (p.Arg655Gln) variant that is recurrent in four individuals. These variants affect evolutionarily conserved amino acids and are located in key functional domains. Gene-specific mutation rate analysis showed that the occurrence of the de novo variants in TRAF7 (p = 2.6 × 10) and the recurrent de novo c.1964G>A (p.Arg655Gln) variant (p = 1.9 × 10) in our exome cohort was unlikely to have occurred by chance. In vitro analyses of the observed TRAF7 mutations showed reduced ERK1/2 phosphorylation. Our findings suggest that missense mutations in TRAF7 are associated with a multisystem disorder and provide evidence of a role for TRAF7 in human development.
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http://dx.doi.org/10.1016/j.ajhg.2018.06.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6035372PMC
July 2018

Clinical Application of Genome and Exome Sequencing as a Diagnostic Tool for Pediatric Patients: a Scoping Review of the Literature.

Genet Med 2019 01 14;21(1):3-16. Epub 2018 May 14.

Texas Children's Hospital, Baylor College of Medicine, Houston, Texas, USA.

Purpose: Availability of clinical genomic sequencing (CGS) has generated questions about the value of genome and exome sequencing as a diagnostic tool. Analysis of reported CGS application can inform uptake and direct further research. This scoping literature review aims to synthesize evidence on the clinical and economic impact of CGS.

Methods: PubMed, Embase, and Cochrane were searched for peer-reviewed articles published between 2009 and 2017 on diagnostic CGS for infant and pediatric patients. Articles were classified according to sample size and whether economic evaluation was a primary research objective. Data on patient characteristics, clinical setting, and outcomes were extracted and narratively synthesized.

Results: Of 171 included articles, 131 were case reports, 40 were aggregate analyses, and 4 had a primary economic evaluation aim. Diagnostic yield was the only consistently reported outcome. Median diagnostic yield in aggregate analyses was 33.2% but varied by broad clinical categories and test type.

Conclusion: Reported CGS use has rapidly increased and spans diverse clinical settings and patient phenotypes. Economic evaluations support the cost-saving potential of diagnostic CGS. Multidisciplinary implementation research, including more robust outcome measurement and economic evaluation, is needed to demonstrate clinical utility and cost-effectiveness of CGS.
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http://dx.doi.org/10.1038/s41436-018-0024-6DOI Listing
January 2019

Gene therapy for repair and regeneration of bone and cartilage.

Curr Opin Pharmacol 2018 06 2;40:59-66. Epub 2018 Apr 2.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA. Electronic address:

Gene therapy refers to the use of viral and non-viral vectors to deliver nucleic acids to tissues of interest using direct (in vivo) or transduced cell-mediated (ex vivo) approaches. Over the past few decades, strategies have been adopted to express therapeutic transgenes at sites of injury to promote or facilitate repair of bone and cartilage. Targets of interest have typically included secreted proteins such as growth factors and anti-inflammatory mediators; however, work has also begun to focus intracellularly on signaling components, transcription factors and small, regulatory nucleic acids such as microRNAs (miRNAs). In recent years, a number of single therapeutic gene approaches (termed 'monotherapies') have proven effective in preclinical models of disease, and several are being evaluated in clinical trials. In particular, an ex vivo TGF-β1 gene therapy was approved in Korea in 2017 for treatment of moderate-to-severe osteoarthritis (OA). The ability to utilize viral vectors for context-specific and combinatorial gene therapy is also being investigated, and these strategies are likely to be important in more robustly addressing the complexities of tissue repair and regeneration in skeletal disease. In this review, we provide an overview of viral gene therapies being developed for treatment of bone and cartilage pathologies, with an emphasis on emerging combinatorial strategies as well as those targeting intracellular mediators such as miRNAs.
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http://dx.doi.org/10.1016/j.coph.2018.03.005DOI Listing
June 2018

mTORC1 Signaling is a Critical Regulator of Postnatal Tendon Development.

Sci Rep 2017 12 7;7(1):17175. Epub 2017 Dec 7.

Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.

Tendons transmit contractile forces between musculoskeletal tissues. Whereas the biomechanical properties of tendons have been studied extensively, the molecular mechanisms regulating postnatal tendon development are not well understood. Here we examine the role of mTORC1 signaling in postnatal tendon development using mouse genetic approaches. Loss of mTORC1 signaling by removal of Raptor in tendons caused severe tendon defects postnatally, including decreased tendon thickness, indicating that mTORC1 is necessary for postnatal tendon development. By contrast, activation of mTORC1 signaling in tendons increased tendon cell numbers and proliferation. In addition, Tsc1 conditional knockout mice presented severely disorganized collagen fibers and neovascularization in the tendon midsubstance. Interestingly, collagen fibril diameter was significantly reduced in both Raptor and Tsc1 conditional knockout mice, albeit with variations in severity. We performed RNA-seq analysis using Achilles tendons to investigate the molecular changes underlying these tendon phenotypes. Raptor conditional knockout mice showed decreased extracellular matrix (ECM) structure-related gene expression, whereas Tsc1 conditional knockout mice exhibited changes in genes regulating TGF-β/BMP/FGF signaling, as well as in genes controlling ECM structure and disassembly. Collectively, our studies suggest that maintaining physiological levels of mTORC1 signaling is essential for postnatal tendon development and maturation.
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http://dx.doi.org/10.1038/s41598-017-17384-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5719403PMC
December 2017

Mutations in Fibronectin Cause a Subtype of Spondylometaphyseal Dysplasia with "Corner Fractures".

Am J Hum Genet 2017 Nov;101(5):815-823

Department of Molecular, Cell, and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA.

Fibronectin is a master organizer of extracellular matrices (ECMs) and promotes the assembly of collagens, fibrillin-1, and other proteins. It is also known to play roles in skeletal tissues through its secretion by osteoblasts, chondrocytes, and mesenchymal cells. Spondylometaphyseal dysplasias (SMDs) comprise a diverse group of skeletal dysplasias and often manifest as short stature, growth-plate irregularities, and vertebral anomalies, such as scoliosis. By comparing the exomes of individuals with SMD with the radiographic appearance of "corner fractures" at metaphyses, we identified three individuals with fibronectin (FN1) variants affecting highly conserved residues. Furthermore, using matching tools and the SkelDys emailing list, we identified other individuals with de novo FN1 variants and a similar phenotype. The severe scoliosis in most individuals and rare developmental coxa vara distinguish individuals with FN1 mutations from those with classical Sutcliffe-type SMD. To study functional consequences of these FN1 mutations on the protein level, we introduced three disease-associated missense variants (p.Cys87Phe [c.260G>T], p.Tyr240Asp [c.718T>G], and p.Cys260Gly [c.778T>G]) into a recombinant secreted N-terminal 70 kDa fragment (rF70K) and the full-length fibronectin (rFN). The wild-type rF70K and rFN were secreted into the culture medium, whereas all mutant proteins were either not secreted or secreted at significantly lower amounts. Immunofluorescence analysis demonstrated increased intracellular retention of the mutant proteins. In summary, FN1 mutations that cause defective fibronectin secretion are found in SMD, and we thus provide additional evidence for a critical function of fibronectin in cartilage and bone.
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http://dx.doi.org/10.1016/j.ajhg.2017.09.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5673654PMC
November 2017

Osteocyte-specific WNT1 regulates osteoblast function during bone homeostasis.

J Clin Invest 2017 Jun 19;127(7):2678-2688. Epub 2017 Jun 19.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA.

Mutations in WNT1 cause osteogenesis imperfecta (OI) and early-onset osteoporosis, identifying it as a key Wnt ligand in human bone homeostasis. However, how and where WNT1 acts in bone are unclear. To address this mechanism, we generated late-osteoblast-specific and osteocyte-specific WNT1 loss- and gain-of-function mouse models. Deletion of Wnt1 in osteocytes resulted in low bone mass with spontaneous fractures similar to that observed in OI patients. Conversely, Wnt1 overexpression from osteocytes stimulated bone formation by increasing osteoblast number and activity, which was due in part to activation of mTORC1 signaling. While antiresorptive therapy is the mainstay of OI treatment, it has limited efficacy in WNT1-related OI. In this study, anti-sclerostin antibody (Scl-Ab) treatment effectively improved bone mass and dramatically decreased fracture rate in swaying mice, a model of global Wnt1 loss. Collectively, our data suggest that WNT1-related OI and osteoporosis are caused in part by decreased mTORC1-dependent osteoblast function resulting from loss of WNT1 signaling in osteocytes. As such, this work identifies an anabolic function of osteocytes as a source of Wnt in bone development and homoeostasis, complementing their known function as targets of Wnt signaling in regulating osteoclastogenesis. Finally, this study suggests that Scl-Ab is an effective genotype-specific treatment option for WNT1-related OI and osteoporosis.
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http://dx.doi.org/10.1172/JCI92617DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5490765PMC
June 2017

A non-mosaic mutation in a male with severe congenital anomalies overlapping focal dermal hypoplasia.

Mol Genet Metab Rep 2017 Sep 7;12:57-61. Epub 2017 Jun 7.

Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.

Mutations in the gene cause the X-linked dominant condition focal dermal hypoplasia (FDH). Features of FDH include striated pigmentation of the skin, ocular and skeletal malformations. FDH is generally associated with lethality in non-mosaic males and most of the currently reported male patients show mosaicism due to post-zygotic mutations in the gene. There is only one previous report of a surviving male with an inherited mutation in the gene. Here, we report two male siblings with multiple malformations including skeletal, ocular and renal defects overlapping with FDH. A novel mutation (p.Ser250Phe) was identified in a non-mosaic, hemizygous state in one of the siblings who survived to 8 years of age. The mother is a heterozygous carrier, has a random X-inactivation pattern and is asymptomatic. Findings unusual for FDH include dysplastic clavicles and bilateral Tessier IV facial clefts. This is the second case report of a non-mosaic mutation in a male individual with multiple congenital anomalies. While the pathogenicity of this mutation remains to be further investigated, the survival of a male with a non-mosaic mutation in is suggestive of a functionally mild mutation leading to an X-linked recessive mode of inheritance.
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http://dx.doi.org/10.1016/j.ymgmr.2017.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466597PMC
September 2017

MicroRNA miR-23a cluster promotes osteocyte differentiation by regulating TGF-β signalling in osteoblasts.

Nat Commun 2017 04 11;8:15000. Epub 2017 Apr 11.

Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA.

Osteocytes are the terminally differentiated cell type of the osteoblastic lineage and have important functions in skeletal homeostasis. Although the transcriptional regulation of osteoblast differentiation has been well characterized, the factors that regulate differentiation of osteocytes from mature osteoblasts are poorly understood. Here we show that miR-23a∼27a∼24-2 (miR-23a cluster) promotes osteocyte differentiation. Osteoblast-specific miR-23a cluster gain-of-function mice have low bone mass associated with decreased osteoblast but increased osteocyte numbers. By contrast, loss-of-function transgenic mice overexpressing microRNA decoys for either miR-23a or miR-27a, but not miR24-2, show decreased osteocyte numbers. Moreover, RNA-sequencing analysis shows altered transforming growth factor-β (TGF-β) signalling. Prdm16, a negative regulator of the TGF-β pathway, is directly repressed by miR-27a with concomitant alteration of sclerostin expression, and pharmacological inhibition of TGF-β rescues the phenotypes observed in the gain-of-function transgenic mice. Taken together, the miR-23a cluster regulates osteocyte differentiation by modulating the TGF-β signalling pathway through targeting of Prdm16.
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http://dx.doi.org/10.1038/ncomms15000DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5394267PMC
April 2017