Publications by authors named "Maria Lisa Dentici"

48 Publications

Clinical delineation, sex differences, and genotype-phenotype correlation in pathogenic KDM6A variants causing X-linked Kabuki syndrome type 2.

Genet Med 2021 Mar 5. Epub 2021 Mar 5.

Division of Evolution & Genomic Sciences, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.

Purpose: The variant spectrum and the phenotype of X-linked Kabuki syndrome type 2 (KS2) are poorly understood.

Methods: Genetic and clinical details of new and published individuals with pathogenic KDM6A variants were compiled and analyzed.

Results: Sixty-one distinct pathogenic KDM6A variants (50 truncating, 11 missense) from 80 patients (34 males, 46 females) were identified. Missense variants clustered in the TRP 2, 3, 7 and Jmj-C domains. Truncating variants were significantly more likely to be de novo. Thirteen individuals had maternally inherited variants and one had a paternally inherited variant. Neonatal feeding difficulties, hypoglycemia, postnatal growth retardation, poor weight gain, motor delay, intellectual disability (ID), microcephaly, congenital heart anomalies, palate defects, renal malformations, strabismus, hearing loss, recurrent infections, hyperinsulinism, seizures, joint hypermobility, and gastroesophageal reflux were frequent clinical findings. Facial features of over a third of patients were not typical for KS. Males were significantly more likely to be born prematurely, have shorter stature, and severe developmental delay/ID.

Conclusion: We expand the KDM6A variant spectrum and delineate the KS2 phenotype. We demonstrate that the variability of the KS2 phenotypic depends on sex and the variant type. We also highlight the overlaps and differences between the phenotypes of KS2 and KS1.
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http://dx.doi.org/10.1038/s41436-021-01119-8DOI Listing
March 2021

SPEN haploinsufficiency causes a neurodevelopmental disorder overlapping proximal 1p36 deletion syndrome with an episignature of X chromosomes in females.

Authors:
Francesca Clementina Radio Kaifang Pang Andrea Ciolfi Michael A Levy Andrés Hernández-García Lucia Pedace Francesca Pantaleoni Zhandong Liu Elke de Boer Adam Jackson Alessandro Bruselles Haley McConkey Emilia Stellacci Stefania Lo Cicero Marialetizia Motta Rosalba Carrozzo Maria Lisa Dentici Kirsty McWalter Megha Desai Kristin G Monaghan Aida Telegrafi Christophe Philippe Antonio Vitobello Margaret Au Katheryn Grand Pedro A Sanchez-Lara Joanne Baez Kristin Lindstrom Peggy Kulch Jessica Sebastian Suneeta Madan-Khetarpal Chelsea Roadhouse Jennifer J MacKenzie Berrin Monteleone Carol J Saunders July K Jean Cuevas Laura Cross Dihong Zhou Taila Hartley Sarah L Sawyer Fabíola Paoli Monteiro Tania Vertemati Secches Fernando Kok Laura E Schultz-Rogers Erica L Macke Eva Morava Eric W Klee Jennifer Kemppainen Maria Iascone Angelo Selicorni Romano Tenconi David J Amor Lynn Pais Lyndon Gallacher Peter D Turnpenny Karen Stals Sian Ellard Sara Cabet Gaetan Lesca Joset Pascal Katharina Steindl Sarit Ravid Karin Weiss Alison M R Castle Melissa T Carter Louisa Kalsner Bert B A de Vries Bregje W van Bon Marijke R Wevers Rolph Pfundt Alexander P A Stegmann Bronwyn Kerr Helen M Kingston Kate E Chandler Willow Sheehan Abdallah F Elias Deepali N Shinde Meghan C Towne Nathaniel H Robin Dana Goodloe Adeline Vanderver Omar Sherbini Krista Bluske R Tanner Hagelstrom Caterina Zanus Flavio Faletra Luciana Musante Evangeline C Kurtz-Nelson Rachel K Earl Britt-Marie Anderlid Gilles Morin Marjon van Slegtenhorst Karin E M Diderich Alice S Brooks Joost Gribnau Ruben G Boers Teresa Robert Finestra Lauren B Carter Anita Rauch Paolo Gasparini Kym M Boycott Tahsin Stefan Barakat John M Graham Laurence Faivre Siddharth Banka Tianyun Wang Evan E Eichler Manuela Priolo Bruno Dallapiccola Lisenka E L M Vissers Bekim Sadikovic Daryl A Scott Jimmy Lloyd Holder Marco Tartaglia

Am J Hum Genet 2021 03 16;108(3):502-516. Epub 2021 Feb 16.

Genetics and Rare Disease Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy. Electronic address:

Deletion 1p36 (del1p36) syndrome is the most common human disorder resulting from a terminal autosomal deletion. This condition is molecularly and clinically heterogeneous. Deletions involving two non-overlapping regions, known as the distal (telomeric) and proximal (centromeric) critical regions, are sufficient to cause the majority of the recurrent clinical features, although with different facial features and dysmorphisms. SPEN encodes a transcriptional repressor commonly deleted in proximal del1p36 syndrome and is located centromeric to the proximal 1p36 critical region. Here, we used clinical data from 34 individuals with truncating variants in SPEN to define a neurodevelopmental disorder presenting with features that overlap considerably with those of proximal del1p36 syndrome. The clinical profile of this disease includes developmental delay/intellectual disability, autism spectrum disorder, anxiety, aggressive behavior, attention deficit disorder, hypotonia, brain and spine anomalies, congenital heart defects, high/narrow palate, facial dysmorphisms, and obesity/increased BMI, especially in females. SPEN also emerges as a relevant gene for del1p36 syndrome by co-expression analyses. Finally, we show that haploinsufficiency of SPEN is associated with a distinctive DNA methylation episignature of the X chromosome in affected females, providing further evidence of a specific contribution of the protein to the epigenetic control of this chromosome, and a paradigm of an X chromosome-specific episignature that classifies syndromic traits. We conclude that SPEN is required for multiple developmental processes and SPEN haploinsufficiency is a major contributor to a disorder associated with deletions centromeric to the previously established 1p36 critical regions.
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http://dx.doi.org/10.1016/j.ajhg.2021.01.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8008487PMC
March 2021

Homozygous and Gene Variants in a Boy with Growth Hormone Deficiency and Early Onset Osteoporosis.

Int J Mol Sci 2021 Jan 13;22(2). Epub 2021 Jan 13.

Laboratory of Medical Genetics, Translational Cytogenomics Research Unit, Bambino Gesù Children Hospital, IRCCS, 00146 Rome, Italy.

We report on a patient born to consanguineous parents, presenting with Growth Hormone Deficiency (GHD) and osteoporosis. SNP-array analysis and exome sequencing disclosed long contiguous stretches of homozygosity and two distinct homozygous variants in (Q6H) and (E1361K) genes. The variant was described as causative in a few subjects with an incompletely penetrant dominant form of combined pituitary hormone deficiency (CPHD). The variant is rare, and so far it has never been found in a homozygous form. Segregation analysis showed that both variants were inherited from heterozygous unaffected parents. Present results further elucidate the inheritance pattern of variants and recommend assessing the clinical impact of variants located in C-terminal propeptide of gene for their potential association with rare recessive and early onset forms of osteoporosis.
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http://dx.doi.org/10.3390/ijms22020750DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7828579PMC
January 2021

Biallelic variants in cause a severe neurodevelopmental disorder with microcephaly, bilateral cataract, epilepsy and simplified gyration.

J Med Genet 2021 Jan 4. Epub 2021 Jan 4.

Medical Genetics Laboratory, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy.

Background: Next-generation sequencing, combined with international pooling of cases, has impressively enhanced the discovery of genes responsible for Mendelian neurodevelopmental disorders, particularly in individuals affected by clinically undiagnosed diseases. To date, biallelic missense variants in gene, encoding a Krüppel-type zinc-finger protein, have been reported in three families with non-syndromic intellectual disability.

Methods: Here, we describe five individuals from four unrelated families with an undiagnosed neurodevelopmental disorder in which we performed exome sequencing, on a combination of trio-based (4 subjects) or single probands (1 subject).

Results: We identified five patients from four unrelated families with homozygous variants by whole exome sequencing. Four had variants resulting in truncation of ZNF526; they were affected by severe prenatal and postnatal microcephaly (ranging from -4 SD to -8 SD), profound psychomotor delay, hypertonic-dystonic movements, epilepsy and simplified gyral pattern on MRI. All of them also displayed bilateral progressive cataracts. A fifth patient had a homozygous missense variant and a slightly less severe disorder, with postnatal microcephaly (-2 SD), progressive bilateral cataracts, severe intellectual disability and unremarkable brain MRI.Mutant zebrafish larvae had notable malformations of the eye and central nervous system, resembling findings seen in the human holoprosencephaly spectrum.

Conclusion: Our findings support the role of biallelic variants in a complex neurodevelopmental disorder, primarily affecting brain and eyes, resulting in severe microcephaly, simplified gyral pattern, epileptic encephalopathy and bilateral cataracts.
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http://dx.doi.org/10.1136/jmedgenet-2020-107430DOI Listing
January 2021

SCUBE3 loss-of-function causes a recognizable recessive developmental disorder due to defective bone morphogenetic protein signaling.

Am J Hum Genet 2021 01 11;108(1):115-133. Epub 2020 Dec 11.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy. Electronic address:

Signal peptide-CUB-EGF domain-containing protein 3 (SCUBE3) is a member of a small family of multifunctional cell surface-anchored glycoproteins functioning as co-receptors for a variety of growth factors. Here we report that bi-allelic inactivating variants in SCUBE3 have pleiotropic consequences on development and cause a previously unrecognized syndromic disorder. Eighteen affected individuals from nine unrelated families showed a consistent phenotype characterized by reduced growth, skeletal features, distinctive craniofacial appearance, and dental anomalies. In vitro functional validation studies demonstrated a variable impact of disease-causing variants on transcript processing, protein secretion and function, and their dysregulating effect on bone morphogenetic protein (BMP) signaling. We show that SCUBE3 acts as a BMP2/BMP4 co-receptor, recruits the BMP receptor complexes into raft microdomains, and positively modulates signaling possibly by augmenting the specific interactions between BMPs and BMP type I receptors. Scube3 mice showed craniofacial and dental defects, reduced body size, and defective endochondral bone growth due to impaired BMP-mediated chondrogenesis and osteogenesis, recapitulating the human disorder. Our findings identify a human disease caused by defective function of a member of the SCUBE family, and link SCUBE3 to processes controlling growth, morphogenesis, and bone and teeth development through modulation of BMP signaling.
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http://dx.doi.org/10.1016/j.ajhg.2020.11.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820739PMC
January 2021

7q11.23 Microduplication Syndrome: Clinical and Neurobehavioral Profiling.

Brain Sci 2020 Nov 11;10(11). Epub 2020 Nov 11.

Child and Adolescent Neuropsychiatry Unit, Department of Neurological and Psychiatric Science, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.

7q11.23 Microduplication (dup7q11.23) syndrome is a rare autosomal dominant disorder due to a recurring 1.5 to 1.8 Mb duplication of the Williams-Beuren Syndrome critical region. Dup7q11.23 has been associated with several neuro-behavioral characteristics such as low cognitive and adaptive functioning, expressive language impairment, anxiety problems and autistic features. In the present study, we analyze the clinical features of ten individuals in which array-CGH detected dup7q11.23, spanning from 1.4 to 2.1 Mb. The clinical characteristics associated with dup7q11.23 are discussed with respect to its reciprocal deletion. Consistent with previous studies, we confirm that individuals with dup7q11.23 syndrome do not have a homogeneous clinical profile, although some recurring dysmorphic features were found, including macrocephaly, prominent forehead, elongated palpebral fissures, thin lip vermilion and microstomia. Minor congenital malformations include patent ductus arteriosus, cryptorchidism and pes planus. A common finding is hypotonia and joint laxity, resulting in mild motor delay. Neuropsychological and psychodiagnostic assessment confirm that mild cognitive impairment, expressive language deficits and anxiety are recurring neurobehavioral features. New insights into adaptive, psychopathological and neurodevelopmental profiles are discussed.
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http://dx.doi.org/10.3390/brainsci10110839DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7697259PMC
November 2020

Atypical 7q11.23 deletions excluding ELN gene result in Williams-Beuren syndrome craniofacial features and neurocognitive profile.

Am J Med Genet A 2021 01 24;185(1):242-249. Epub 2020 Oct 24.

Bambino Gesù Children Hospital, IRCCS, Rome, Italy.

Williams-Beurens syndrome (WBS) is a rare genetic disorder caused by a recurrent 7q11.23 microdeletion. Clinical characteristics include typical facial dysmorphisms, weakness of connective tissue, short stature, mild to moderate intellectual disability and distinct behavioral phenotype. Cardiovascular diseases are common due to haploinsufficiency of ELN gene. A few cases of larger or smaller deletions have been reported spanning towards the centromeric or the telomeric regions, most of which included ELN gene. We report on three patients from two unrelated families, presenting with distinctive WBS features, harboring an atypical distal deletion excluding ELN gene. Our study supports a critical role of CLIP2, GTF2IRD1, and GTF2I gene in the WBS neurobehavioral profile and in craniofacial features, highlights a possible role of HIP1 in the autism spectrum disorder, and delineates a subgroup of WBS individuals with an atypical distal deletion not associated to an increased risk of cardiovascular defects.
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http://dx.doi.org/10.1002/ajmg.a.61937DOI Listing
January 2021

PPP1R21-related syndromic intellectual disability: Report of an adult patient and review.

Am J Med Genet A 2020 12 27;182(12):3014-3022. Epub 2020 Sep 27.

Scientific Directorate, Bambino Gesù Pediatric Hospital, IRCCS, Rome, Italy.

Variants in PPP1R21 were recently found to be associated with an autosomal recessive intellectual disability syndrome in 9 individuals. Our patient, the oldest among the known subjects affected by PPP1R21-related syndrome, manifested intellectual disability, short stature, congenital ataxia with cerebellar vermis hypoplasia, generalized hypertrichosis, ulcerative keratitis, muscle weakness, progressive coarse appearance, macroglossia with fissured tongue, and deep palmar and plantar creases. We provide an overview of the clinical spectrum and natural history of this newly recognized disorder, arguing the emerging notion that PPP1R21 gene mutations could result in endolysosomal functional defects. The oldest patients could display a more severe clinical outcome, due to accumulation of metabolites or damage secondary to an alteration of the autophagy pathway. Follow-up of patients with PPP1R21 mutations is recommended for improving the understanding of PPP1R21-related syndromic intellectual disability.
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http://dx.doi.org/10.1002/ajmg.a.61889DOI Listing
December 2020

GRIA3 missense mutation is cause of an x-linked developmental and epileptic encephalopathy.

Seizure 2020 Nov 22;82:1-6. Epub 2020 Sep 22.

Rare and Epilepsies Unit, Department of Neurological Science, Bambino Gesù Children's Hospital, IRCCS, Full Member of European Reference Network EpiCARE, Rome, Italy. Electronic address:

Purpose: GRIA3, encoding subunit 3 of glutamate ionotropic AMPA receptor, is associated with X-linked intellectual disability (ID), dysmorphic features, and non-syndromic epilepsy. We aimed to characterize electro-clinical features of patients with GRIA3 variants.

Methods: We report a patient carrying a hemizygous missense variant c.2359 G > A (p.Glu787Lys) inGRIA3 gene. Following a literature search, we also reviewed clinical, electrophysiological, radiological, and genetic features of 19 patients with GRIA3 mutations.

Results: This 26-month-old boy had developmental delay, early onset refractory myoclonic epilepsy, and non-convulsive refractory status epilepticus. In published reports, epilepsy was in 6 of 19 patients carrying different genotypes, though epilepsy and electroencephalogram features were not completely defined. Out of the 6 patients, one presented with generalized tonic-clonic seizures, two with myoclonic and clonic events (one also presented with epileptic spasms), and one with atypical absences and myoclonic jerks. Information on type of epilepsy was unavailable for 3 cases. Epilepsy onset was early in life and there was potential tendency for myoclonic/clonic events. The epilepsy was difficult to treat and prognosis is poor. Severity of ID ranged from mild to severe and was variably associated with bipolar affective disorder and autistic spectrum disorders. Other neurological features included hypotonia, asthenic body habitus with poor muscle bulk, and hyporeflexia.

Conclusion: Our report expands knowledge on the electro-clinical and molecular spectrum of GRIA3 variants. Larger investigations will better define the prevalence of epilepsy, the epileptic phenotype, and syndromic features underlying GRIA3 variants.
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http://dx.doi.org/10.1016/j.seizure.2020.08.032DOI Listing
November 2020

Cantú syndrome versus Zimmermann-Laband syndrome: Report of nine individuals with ABCC9 variants.

Eur J Med Genet 2020 Sep 2;63(9):103996. Epub 2020 Jul 2.

Institute of Human Genetics, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. Electronic address:

Cantú syndrome (CS) is a rare developmental disorder characterized by a coarse facial appearance, macrocephaly, hypertrichosis, skeletal and cardiovascular anomalies and caused by heterozygous gain-of-function variants in ABCC9 and KCNJ8, encoding subunits of heterooctameric ATP-sensitive potassium (K) channels. CS shows considerable clinical overlap with Zimmermann-Laband syndrome (ZLS), a rare condition with coarse facial features, hypertrichosis, gingival overgrowth, intellectual disability of variable degree, and hypoplasia or aplasia of terminal phalanges and/or nails. ZLS is caused by heterozygous gain-of-function variants in KCNH1 or KCNN3, and gain-of-function KCNK4 variants underlie the clinically similar FHEIG (facial dysmorphism, hypertrichosis, epilepsy, intellectual disability/developmental delay, and gingival overgrowth) syndrome; KCNH1, KCNN3 and KCNK4 encode potassium channels. Within our research project on ZLS, we performed targeted Sanger sequencing of ABCC9 in 15 individuals tested negative for a mutation in the ZLS-associated genes and found two individuals harboring a heterozygous pathogenic ABCC9 missense variant. Through a collaborative effort, we identified a total of nine individuals carrying a monoallelic ABCC9 variant: five sporadic patients and four members of two unrelated families. Among the six detected ABCC9 missense variants, four [p.(Pro252Leu), p.(Thr259Lys), p.(Ala1064Pro), and p.(Arg1197His)] were novel. Systematic assessment of the clinical features in the nine cases with an ABCC9 variant highlights the significant clinical overlap between ZLS and CS that includes early developmental delay, hypertrichosis, gingival overgrowth, joint laxity, and hypoplasia of terminal phalanges and nails. Gain of K channel activity possibly accounts for significant clinical similarities of CS, ZLS and FHEIG syndrome and defines a new subgroup of potassium channelopathies.
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http://dx.doi.org/10.1016/j.ejmg.2020.103996DOI Listing
September 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 Medical Genetics, Department of Pediatrics, CHU Sainte-Justine, University of Montreal, Montreal, QC, Canada.

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

A new 1p36.13-1p36.12 microdeletion syndrome characterized by learning disability, behavioral abnormalities, and ptosis.

Clin Genet 2020 06 1;97(6):927-932. Epub 2020 Apr 1.

Department of Clinical Genetics, Odense University Hospital, Odense, Denmark.

Two 1p36 contiguous gene deletion syndromes are known so far: the terminal 1p36 deletion syndrome and a 1p36 deletion syndrome with a critical region located more proximal at 1p36.23-1p36.22. We present even more proximally located overlapping deletions from seven individuals, with the smallest region of overlap comprising 1 Mb at 1p36.13-1p36.12 (chr1:19077793-20081292 (GRCh37/hg19)) defining a new contiguous gene deletion syndrome. The characteristic features of this new syndrome are learning disability or mild intellectual disability, speech delay, behavioral abnormalities, and ptosis. The genes UBR4 and CAPZB are considered the most likely candidate genes for the features of this new syndrome.
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http://dx.doi.org/10.1111/cge.13739DOI Listing
June 2020

Co-occurrence of mutations in KIF7 and KIAA0556 in Joubert syndrome with ocular coloboma, pituitary malformation and growth hormone deficiency: a case report and literature review.

BMC Pediatr 2020 03 12;20(1):120. Epub 2020 Mar 12.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Viale di San Paolo 15, 00146, Rome, Italy.

Background: Joubert syndrome is a recessive neurodevelopmental disorder characterized by clinical and genetic heterogeneity. Clinical hallmarks include hypotonia, ataxia, facial dysmorphism, abnormal eye movement, irregular breathing pattern cognitive impairment and, the molar tooth sign is the pathognomonic midbrain-hindbrain malformation on magnetic resonance imaging. The disorder is predominantly caused by biallelic mutations in more than 30 genes encoding proteins with a pivotal role in morphology and function of the primary cilium. Oligogenic inheritance or occurrence of genetic modifiers has been suggested to contribute to the variability of the clinical phenotype. We report on a family with peculiar clinical spectrum Joubert syndrome molecularly and clinically dissecting a complex phenotype, in which hypogonadism, pituitary malformation and growth hormone deficiency occur as major features.

Case Presentation: A 7 year-old male was enrolled in a dedicated "Undiagnosed Patients Program" for a peculiar form of Joubert syndrome complicated by iris and retinochoroidal coloboma, hypogonadism pituitary malformation, and growth hormone deficiency. The molecular basis of the complex phenotype was investigated by whole exome sequencing. The concomitant occurrence of homozygosity for mutations in KIF7 and KIAA0556 was identified, and the assessment of major clinical features associated with mutations in these two genes provided evidence that these two independent events represent the cause underlying the complexity of the present clinical phenotype.

Conclusion: Beside the clinical variability of Joubert syndrome, co-occurrence of mutations in ciliopathy-associated genes may contribute to increase the clinical complexity of the trait.
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http://dx.doi.org/10.1186/s12887-020-2019-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7066839PMC
March 2020

KBG syndrome: Common and uncommon clinical features based on 31 new patients.

Am J Med Genet A 2020 05 3;182(5):1073-1083. Epub 2020 Mar 3.

Laboratory of Medical Genetics, Medical Genetics, Rare Diseases, Pediatric Cardiology, and Endocrinology Units, Scientific Rectorate, Bambino Gesù Pediatric Hospital, IRCCS, Rome, Italy.

KBG syndrome (MIM #148050) is an autosomal dominant disorder characterized by developmental delay, intellectual disability, distinct craniofacial anomalies, macrodontia of permanent upper central incisors, skeletal abnormalities, and short stature. This study describes clinical features of 28 patients, confirmed by molecular testing of ANKRD11 gene, and three patients with 16q24 deletion encompassing ANKRD11 gene, diagnosed in a single center. Common clinical features are reported, together with uncommon findings, clinical expression in the first years of age, distinctive associations, and familial recurrences. Unusual manifestations emerging from present series include juvenile idiopathic arthritis, dysfunctional dysphonia, multiple dental agenesis, idiopathic precocious telarche, oral frenula, motor tics, and lipoma of corpus callosum, pilomatrixoma, and endothelial corneal polymorphic dystrophy. Facial clinical markers suggesting KBG syndrome before 6 years of age include ocular and mouth conformation, wide eyebrows, synophrys, long black eyelashes, long philtrum, thin upper lip. General clinical symptoms leading to early genetic evaluation include developmental delay, congenital malformations, hearing anomalies, and feeding difficulties. It is likely that atypical clinical presentation and overlapping features in patients with multiple variants are responsible for underdiagnosis in KBG syndrome. Improved knowledge of common and atypical features of this disorder improves clinical management.
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http://dx.doi.org/10.1002/ajmg.a.61524DOI Listing
May 2020

TUBB Variants Underlying Different Phenotypes Result in Altered Vesicle Trafficking and Microtubule Dynamics.

Int J Mol Sci 2020 Feb 18;21(4). Epub 2020 Feb 18.

Unit of Neuromuscular and Neurodegenerative Disorders, Department Neurosciences, Bambino Gesù Children's Hospital, IRCCS 00146 Rome, Italy.

Tubulinopathies are rare neurological disorders caused by alterations in tubulin structure and function, giving rise to a wide range of brain abnormalities involving neuronal proliferation, migration, differentiation and axon guidance. TUBB is one of the ten β-tubulin encoding genes present in the human genome and is broadly expressed in the developing central nervous system and the skin. Mutations in TUBB are responsible for two distinct pathological conditions: the first is characterized by microcephaly and complex structural brain malformations and the second, also known as "circumferential skin creases Kunze type" (CSC-KT), is associated to neurological features, excess skin folding and growth retardation. We used a combination of immunocytochemical and cellular approaches to explore, on patients' derived fibroblasts, the functional consequences of two TUBB variants: the novel mutation (p.N52S), associated with basal ganglia and cerebellar dysgenesis, and the previously reported variant (p.M73T), linked to microcephaly, corpus callosum agenesis and CSC-KT skin phenotype. Our results demonstrate that these variants impair microtubule (MT) function and dynamics. Most importantly, our studies show an altered epidermal growth factor (EGF) and transferrin (Tf) intracellular vesicle trafficking in both patients' fibroblasts, suggesting a specific role of TUBB in MT-dependent vesicular transport.
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http://dx.doi.org/10.3390/ijms21041385DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7073044PMC
February 2020

Infantile-Onset Syndromic Cerebellar Ataxia and CACNA1G Mutations.

Pediatr Neurol 2020 03 19;104:40-45. Epub 2019 Oct 19.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.

Background: Congenital ataxias associated with cerebellar atrophy are clinically heterogeneous conditions with a variable age of onset and a diverse molecular basis. The hypothesis-free approach of genomic sequencing has led to the discovery of new genes implicated in these disorders and the identification of unexpected genotype-phenotype correlations. Although a recurrent heterozygous mutation (p.Arg1715His) in CACNA1G is known to cause adult-onset spinocerebellar ataxia 42 (SCA42*616795), gain-of-function mutations in this gene have recently been identified by whole exome sequencing (WES) in four children with cerebellar atrophy and ataxia, psychomotor delay, and other variable features.

Methods: We describe four children from unrelated families with cerebellar anomalies on magnetic resonance imaging (atrophy or hypoplasia of the cerebellar vermis), hypertonia, psychomotor and speech delay, severe intellectual disability, ophthalmologic features and peculiar dysmorphic traits. All patients underwent a trio-based WES analysis. Clinical records were used to characterize the clinical profile of this newly recognized disorder.

Results: Two previously reported de novo disease-causing mutations in CACNA1G (c.2881G>A, p.Ala961Thr and c.4591A>G, p.Met1531Val) were identified in these patients, providing further evidence of the specific impact of these variants. All four patients exhibit distinctive dysmorphic and ectodermal features which overlap those of the previously reported patients, allowing us to define the major features characterizing this homogeneous neurodevelopmental syndromic disorder associated with upregulated CACNA1G function.

Conclusion: Our findings confirm the specific association between a narrow spectrum of missense mutations in CACNA1G and a novel syndrome with infantile-onset cerebellar ataxiaand provide a dysmorphologic delineation of this novel neurodevelopmental trait.
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http://dx.doi.org/10.1016/j.pediatrneurol.2019.09.005DOI Listing
March 2020

De Novo Variants Disturbing the Transactivation Capacity of POU3F3 Cause a Characteristic Neurodevelopmental Disorder.

Am J Hum Genet 2019 08 11;105(2):403-412. Epub 2019 Jul 11.

Language and Genetics Department, Max Planck Institute for Psycholinguistics, PO Box 310, 6500AH Nijmegen, the Netherlands; Donders Institute for Brain, Cognition, and Behaviour, PO Box 9104, 6500HE Nijmegen, the Netherlands. Electronic address:

POU3F3, also referred to as Brain-1, is a well-known transcription factor involved in the development of the central nervous system, but it has not previously been associated with a neurodevelopmental disorder. Here, we report the identification of 19 individuals with heterozygous POU3F3 disruptions, most of which are de novo variants. All individuals had developmental delays and/or intellectual disability and impairments in speech and language skills. Thirteen individuals had characteristic low-set, prominent, and/or cupped ears. Brain abnormalities were observed in seven of eleven MRI reports. POU3F3 is an intronless gene, insensitive to nonsense-mediated decay, and 13 individuals carried protein-truncating variants. All truncating variants that we tested in cellular models led to aberrant subcellular localization of the encoded protein. Luciferase assays demonstrated negative effects of these alleles on transcriptional activation of a reporter with a FOXP2-derived binding motif. In addition to the loss-of-function variants, five individuals had missense variants that clustered at specific positions within the functional domains, and one small in-frame deletion was identified. Two missense variants showed reduced transactivation capacity in our assays, whereas one variant displayed gain-of-function effects, suggesting a distinct pathophysiological mechanism. In bioluminescence resonance energy transfer (BRET) interaction assays, all the truncated POU3F3 versions that we tested had significantly impaired dimerization capacities, whereas all missense variants showed unaffected dimerization with wild-type POU3F3. Taken together, our identification and functional cell-based analyses of pathogenic variants in POU3F3, coupled with a clinical characterization, implicate disruptions of this gene in a characteristic neurodevelopmental disorder.
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http://dx.doi.org/10.1016/j.ajhg.2019.06.007DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698880PMC
August 2019

9q34.3 microduplications lead to neurodevelopmental disorders through EHMT1 overexpression.

Neurogenetics 2019 08 17;20(3):145-154. Epub 2019 Jun 17.

Research Lab of Medical Cytogenetics and Molecular Genetics, Istituto Auxologico Italiano, IRCCS, 20145, Milan, Italy.

Both copy number losses and gains occur within subtelomeric 9q34 region without common breakpoints. The microdeletions cause Kleefstra syndrome (KS), whose responsible gene is EHMT1. A 9q34 duplication syndrome (9q34 DS) had been reported in literature, but it has never been characterized by a detailed molecular analysis of the gene content and endpoints. To the best of our knowledge, we report on the first patient carrying the smallest 9q34.3 duplication containing EHMT1 as the only relevant gene. We compared him with 21 reported patients described here as carrying 9q34.3 duplications encompassing the entire gene and extending within ~ 3 Mb. By surveying the available clinical and molecular cytogenetic data, we were able to discover that similar neurodevelopmental disorders (NDDs) were shared by patient carriers of even very differently sized duplications. Moreover, some facial features of the 9q34 DS were more represented than those of KS. However, an accurate in silico analysis of the genes mapped in all the duplications allowed us to support EHMT1 as being sufficient to cause a NDD phenotype. Wider patient cohorts are needed to ascertain whether the rearrangements have full causative role or simply confer the susceptibility to NDDs and possibly to identify the cognitive and behavioral profile associated with the increased dosage of EHMT1.
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http://dx.doi.org/10.1007/s10048-019-00581-6DOI Listing
August 2019

Familial aggregation of "apple peel" intestinal atresia and cardiac left-sided obstructive lesions: A possible causal relationship with NOTCH1 gene mutations.

Am J Med Genet A 2019 08 20;179(8):1570-1574. Epub 2019 May 20.

Medical Genetics Unit, Medical Genetics Laboratory, Neonatal Surgery Unit, Neonatal Intensive Care Unit, Scientific Rectorate, Bambino Gesù Pediatric Hospital, IRCCS, Rome, Italy.

"Apple peel" intestinal atresia is a rare form of small bowel atresia, in which the duodenum or proximal jejunum ends in a blind pouch and the distal small bowel wraps around its vascular supply, in a spiral resembling an apple peel. The etiology of "apple peel" intestinal atresia is presently unknown, although a congenital or acquired intestinal vascular accident can have a role in the pathogenesis. We report a family in which the proband affected by "apple peel" intestinal atresia, had a sibling (an interrupted pregnancy), and a paternal cousin with cardiac left-sided obstructive lesions. Molecular testing for NOTCH1 gene was carried out in the proband, because pathogenic mutations in this gene have been associated with familial and sporadic cardiac left-sided obstructive lesions and vascular anomalies, both isolated or within the spectrum of the Adams-Oliver syndrome (AOS). The heterozygous c.2734C>T (p.Arg912Trp) NOTCH1 variant was found in the proband with "apple peel" intestinal atresia and in his father. This result argues for a possible causal relationship between NOTCH1 gene mutations and some forms of intestinal defects, through a vascular mechanism. The spectrum of NOTCH1-associated malformations is widened. Genetic counseling should take into account intrafamilial variable clinical expression and incomplete penetrance.
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http://dx.doi.org/10.1002/ajmg.a.61195DOI Listing
August 2019

Mutation update for the SATB2 gene.

Hum Mutat 2019 08 18;40(8):1013-1029. Epub 2019 Jun 18.

Department of Biological Sciences, University of Massachusetts Lowell, Lowell, Massachusetts.

SATB2-associated syndrome (SAS) is an autosomal dominant neurodevelopmental disorder caused by alterations in the SATB2 gene. Here we present a review of published pathogenic variants in the SATB2 gene to date and report 38 novel alterations found in 57 additional previously unreported individuals. Overall, we present a compilation of 120 unique variants identified in 155 unrelated families ranging from single nucleotide coding variants to genomic rearrangements distributed throughout the entire coding region of SATB2. Single nucleotide variants predicted to result in the occurrence of a premature stop codon were the most commonly seen (51/120 = 42.5%) followed by missense variants (31/120 = 25.8%). We review the rather limited functional characterization of pathogenic variants and discuss current understanding of the consequences of the different molecular alterations. We present an expansive phenotypic review along with novel genotype-phenotype correlations. Lastly, we discuss current knowledge of animal models and present future prospects. This review should help provide better guidance for the care of individuals diagnosed with SAS.
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http://dx.doi.org/10.1002/humu.23771DOI Listing
August 2019

Confirmation of BRD4 haploinsufficiency role in Cornelia de Lange-like phenotype and delineation of a 19p13.12p13.11 gene contiguous syndrome.

Ann Hum Genet 2019 03 10;83(2):100-109. Epub 2018 Oct 10.

Medical Genetics Department, Bambino Gesù Children's Hospital, Rome, Italy.

Cornelia de Lange syndrome (CdLS) is a genetically and clinical heterogeneous condition characterized by congenital malformation, intellectual disability, and peculiar dysmorphic features. Recently, BRD4 (19p13.12) was proposed as a new critical gene associated with a mild CdLS because of a similar presentation of the patients carrying point mutations and of its involvement in the NIPBL pathway. Patients harboring a 19p interstitial deletion shared some physical features with BRD4 mutation carriers, which results in a more complex phenotype because of the involvement of several neighboring genes. We report a new 19p deletion in a patient clinically diagnosed as CdLS, partially overlapping with previously published cases with the aim to support the role of BRD4 haploinsufficiency in a CdL-like phenotype and to improve the delineation of 19p13.12p13.11 deletion as a new nonrecurrent gene contiguous syndrome, spanning GIPC1, NOTCH3, BRD4, AKAP8, AKAP8L, CASP14, and EPS15L1 genes. Previously described cases are reviewed, attempting to delineate a genotype-phenotype correlation.
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http://dx.doi.org/10.1111/ahg.12289DOI Listing
March 2019

Mutations in KCNK4 that Affect Gating Cause a Recognizable Neurodevelopmental Syndrome.

Am J Hum Genet 2018 10;103(4):621-630

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, 00146 Rome, Italy. Electronic address:

Aberrant activation or inhibition of potassium (K) currents across the plasma membrane of cells has been causally linked to altered neurotransmission, cardiac arrhythmias, endocrine dysfunction, and (more rarely) perturbed developmental processes. The K channel subfamily K member 4 (KCNK4), also known as TRAAK (TWIK-related arachidonic acid-stimulated K channel), belongs to the mechano-gated ion channels of the TRAAK/TREK subfamily of two-pore-domain (K2P) K channels. While K2P channels are well known to contribute to the resting membrane potential and cellular excitability, their involvement in pathophysiological processes remains largely uncharacterized. We report that de novo missense mutations in KCNK4 cause a recognizable syndrome with a distinctive facial gestalt, for which we propose the acronym FHEIG (facial dysmorphism, hypertrichosis, epilepsy, intellectual disability/developmental delay, and gingival overgrowth). Patch-clamp analyses documented a significant gain of function of the identified KCNK4 channel mutants basally and impaired sensitivity to mechanical stimulation and arachidonic acid. Co-expression experiments indicated a dominant behavior of the disease-causing mutations. Molecular dynamics simulations consistently indicated that mutations favor sealing of the lateral intramembrane fenestration that has been proposed to negatively control K flow by allowing lipid access to the central cavity of the channel. Overall, our findings illustrate the pleiotropic effect of dysregulated KCNK4 function and provide support to the hypothesis of a gating mechanism based on the lateral fenestrations of K2P channels.
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http://dx.doi.org/10.1016/j.ajhg.2018.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174320PMC
October 2018

TARP syndrome: Long-term survival, anatomic patterns of congenital heart defects, differential diagnosis and pathogenetic considerations.

Eur J Med Genet 2019 Jun 3;62(6):103534. Epub 2018 Sep 3.

Medical Genetics, Department of Pediatrics, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

TARP syndrome (TARPS) is an X-linked syndromic condition including Robin sequence, congenital heart defects, developmental delay, feeding difficulties and talipes equinovarus, as major features. The disease is caused by inactivating mutations in RBM10 which encodes for a RNA binding motif protein involved in transcript processing. We herein report a male born from healthy and non-consanguineous parents, presenting prenatal record of intrauterine fetal growth retardation, and postnatal features including growth and developmental delays, CNS abnormalities, facial dysmorphisms, bilateral syndactyly at the hands, talipes equinovarus and congenital heart defects. By using trio-based Whole Exome Sequencing approach, a maternally inherited RBM10 frameshift variant causing decay of the RBM10 transcript was identified. Despite the syndrome is considered lethal in affected males, our subject with molecularly confirmed TARPS is still alive at 11 years of age supporting the chance of surviving. Long-term surviving in TARPS is extremely rare and should be considered in genetic counselling and clinical follow up of the syndrome. We provide the natural history of the syndrome, reviewing the major clinical characteristics. Congenital heart defects are confirmed as specific diagnostic markers for the syndrome. In addition, cardiac anatomical details are defining a possible clinical overlap with syndromic conditions related to the hedgehog pathway and/or primary cilium anomalies as Oral-Facial-Digital or Smith-Lemli-Opitz syndromes.
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http://dx.doi.org/10.1016/j.ejmg.2018.09.001DOI Listing
June 2019

A Child with Diminished Linear Growth and Waddling Gait.

J Pediatr 2018 10 8;201:297-297.e1. Epub 2018 May 8.

University of Trieste Trieste, Italy; Pediatrics Institute for Maternal and Child Health-IRCCS "Burlo Garofolo" Trieste, Italy.

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http://dx.doi.org/10.1016/j.jpeds.2018.04.007DOI Listing
October 2018

Delineating the psychiatric and behavioral phenotype of recurrent 2q13 deletions and duplications.

Am J Med Genet B Neuropsychiatr Genet 2018 06 31;177(4):397-405. Epub 2018 Mar 31.

Molecular Psychiatry Laboratory, Division of Psychiatry, University College London, London, United Kingdom.

Recurrent deletions and duplications at the 2q13 locus have been associated with developmental delay (DD) and dysmorphisms. We aimed to undertake detailed clinical characterization of individuals with 2q13 copy number variations (CNVs), with a focus on behavioral and psychiatric phenotypes. Participants were recruited via the Unique chromosomal disorder support group, U.K. National Health Service Regional Genetics Centres, and the DatabasE of genomiC varIation and Phenotype in Humans using Ensembl Resources (DECIPHER) database. A review of published 2q13 patient case reports was undertaken to enable combined phenotypic analysis. We present a new case series of 2q13 CNV carriers (21 deletion, 4 duplication) and the largest ever combined analysis with data from published studies, making a total of 54 deletion and 23 duplication carriers. DD/intellectual disabilities was identified in the majority of carriers (79% deletion, 70% duplication), although in the new cases 52% had an IQ in the borderline or normal range. Despite the median age of the new cases being only 9 years, 64% had a clinical psychiatric diagnosis. Combined analysis found attention deficit hyperactivity disorder (ADHD) to be the most frequent diagnosis (48% deletion, 60% duplication), followed by autism spectrum disorders (33% deletion, 17% duplication). Aggressive (33%) and self-injurious behaviors (33%) were also identified in the new cases. CNVs at 2q13 are typically associated with DD with mildly impaired intelligence, and a high rate of childhood psychiatric diagnoses-particularly ADHD. We have further characterized the clinical phenotype related to imbalances of the 2q13 region and identified it as a region of interest for the neurobiological investigation of ADHD.
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http://dx.doi.org/10.1002/ajmg.b.32627DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001478PMC
June 2018

Congenital heart defects in molecularly proven Kabuki syndrome patients.

Am J Med Genet A 2017 Nov 8;173(11):2912-2922. Epub 2017 Sep 8.

Medical Genetics Unit, Medical Genetics Laboratory, Pediatric Cardiology, Bambino Gesù Pediatric Hospital, IRCCS, Rome, Italy.

The prevalence of congenital heart defects (CHD) in Kabuki syndrome ranges from 28% to 80%. Between January 2012 and December 2015, 28 patients had a molecularly proven diagnosis of Kabuki syndrome. Pathogenic variants in KMT2D (MLL2) were detected in 27 patients, and in KDM6A gene in one. CHD was diagnosed in 19/27 (70%) patients with KMT2D (MLL2) variant, while the single patient with KDM6A change had a normal heart. The anatomic types among patients with CHD included aortic coarctation (4/19 = 21%) alone or associated with an additional CHD, bicuspid aortic valve (4/19 = 21%) alone or associated with an additional CHD, perimembranous subaortic ventricular septal defect (3/19 = 16%), atrial septal defect ostium secundum type (3/19 = 16%), conotruncal heart defects (3/19 = 16%). Additional CHDs diagnosed in single patients included aortic dilatation with mitral anomaly and hypoplastic left heart syndrome. We also reviewed CHDs in patients with a molecular diagnosis of Kabuki syndrome reported in the literature. In conclusion, a CHD is detected in 70% of patients with KMT2D (MLL2) pathogenic variants, most commonly left-sided obstructive lesions, including multiple left-sided obstructions similar to those observed in the spectrum of the Shone complex, and septal defects. Clinical management of Kabuki syndrome should include echocardiogram at the time of diagnosis, with particular attention to left-sided obstructive lesions and mitral anomalies, and annual monitoring for aortic arch dilatation.
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http://dx.doi.org/10.1002/ajmg.a.38417DOI Listing
November 2017

Identification of novel and hotspot mutations in the channel domain of ITPR1 in two patients with Gillespie syndrome.

Gene 2017 Sep 8;628:141-145. Epub 2017 Jul 8.

Unit of Neuromuscular and Neurodegenerative Disorders, Laboratory of Molecular Medicine, Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy. Electronic address:

ITPR1 encodes an intracellular receptor for inositol 1,4,5-trisphosphate (InsP3) which is highly expressed in the cerebellum and is involved in the regulation of Ca2+ homeostasis. Missense mutations in the InsP3-binding domain (IRBIT) of ITPR1 are frequently associated with early onset cerebellar atrophy. Gillespie syndrome is characterized by congenital ataxia, mild to moderate intellectual disability and iris hypoplasia. Dominant or recessive ITPR1 mutations have been recently associated with this form of syndromic ataxia. We performed next generation sequencing in two simplex families with Gillespie syndrome and identified de novo pathological mutations localized in the C-terminal channel domain of ITPR1 in both patients: a recurrent deletion (p.Lys2596del) and a novel missense mutation (p.Asn2576Ile) close to a point of constriction in the Ca pore. Our study expands the mutational spectrum of ITPR1 and confirms that ITPR1 screening should be implemented in patients with congenital cerebellar ataxia with or without iris hypoplasia.
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http://dx.doi.org/10.1016/j.gene.2017.07.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5607352PMC
September 2017

Expanding the phenotypic spectrum of truncating POGZ mutations: Association with CNS malformations, skeletal abnormalities, and distinctive facial dysmorphism.

Am J Med Genet A 2017 Jul 7;173(7):1965-1969. Epub 2017 May 7.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, IRCCS, Rome, Italy.

Exome sequencing has led to the comprehension of the molecular bases of several forms of neurodevelopmental disorders, a clinically heterogeneous group of diseases characterized by intellectual disability (ID) and autism spectrum disorder (ASD). De novo mutations in POGZ has been causally linked to isolated ASD and syndromic ID, only recently. Here we report on a 15 year-old girl in whom exome sequencing allowed to identify a de novo POGZ truncating mutation as the molecular cause underlying a complex phenotype apparently not fitting any recognized syndrome. We describe the evolution of her clinical features with age, and review published clinical data of patients with POGZ mutations to systematically analyze the clinical spectrum associated with mutations. Our finding expands the clinical and molecular spectrum of POGZ mutations. Revision of the literature indicate that moderate to severe ID, microcephaly, variable CNS malformations, reduced growth, brachytelephalangy, and facial dysmorphism represent recurrent features associated with POGZ mutations.
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http://dx.doi.org/10.1002/ajmg.a.38255DOI Listing
July 2017

Clinical spectrum of Kabuki-like syndrome caused by HNRNPK haploinsufficiency.

Clin Genet 2018 02 25;93(2):401-407. Epub 2017 Apr 25.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, Rome, Italy.

Kabuki syndrome is a genetically heterogeneous disorder characterized by postnatal growth retardation, skeletal abnormalities, intellectual disability, facial dysmorphisms and a variable range of organ malformations. In ~30% of affected individuals, the underlying genetic defect remains unknown. A small number of inactivating heterozygous HNRNPK mutations has recently been reported to be associated with a condition partially overlapping or suggestive of Kabuki syndrome. Here, we report on an 11-year-old girl with a complex phenotype in whom the diagnosis of KS was suggested but molecular testing for the known causative disease genes was negative. Whole-exome sequencing identified a previously undescribed de novo truncating mutation in HNRNPK as the molecular defect underlying the trait. Analysis of available records of patients with HNRNPK haploinsufficiency was performed to delineate the associated clinical phenotype and outline their distinguishing features in comparison with the KS clinical spectrum. The clinical profile associated with inactivating HNRNPK mutations supports the idea that the associated disorder should be considered as a distinct nosologic entity clinically related to KS, and that the condition should be considered in differential diagnosis with KS, in particular in subjects exhibiting brain malformation (nodular heterotopia), craniosynostosis, and polydactyly.
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http://dx.doi.org/10.1111/cge.13029DOI Listing
February 2018

Biallelic Mutations in TBCD, Encoding the Tubulin Folding Cofactor D, Perturb Microtubule Dynamics and Cause Early-Onset Encephalopathy.

Am J Hum Genet 2016 Oct 22;99(4):962-973. Epub 2016 Sep 22.

Genetics and Rare Diseases Research Division, Ospedale Pediatrico Bambino Gesù, Rome 00146, Italy. Electronic address:

Microtubules are dynamic cytoskeletal elements coordinating and supporting a variety of neuronal processes, including cell division, migration, polarity, intracellular trafficking, and signal transduction. Mutations in genes encoding tubulins and microtubule-associated proteins are known to cause neurodevelopmental and neurodegenerative disorders. Growing evidence suggests that altered microtubule dynamics may also underlie or contribute to neurodevelopmental disorders and neurodegeneration. We report that biallelic mutations in TBCD, encoding one of the five co-chaperones required for assembly and disassembly of the αβ-tubulin heterodimer, the structural unit of microtubules, cause a disease with neurodevelopmental and neurodegenerative features characterized by early-onset cortical atrophy, secondary hypomyelination, microcephaly, thin corpus callosum, developmental delay, intellectual disability, seizures, optic atrophy, and spastic quadriplegia. Molecular dynamics simulations predicted long-range and/or local structural perturbations associated with the disease-causing mutations. Biochemical analyses documented variably reduced levels of TBCD, indicating relative instability of mutant proteins, and defective β-tubulin binding in a subset of the tested mutants. Reduced or defective TBCD function resulted in decreased soluble α/β-tubulin levels and accelerated microtubule polymerization in fibroblasts from affected subjects, demonstrating an overall shift toward a more rapidly growing and stable microtubule population. These cells displayed an aberrant mitotic spindle with disorganized, tangle-shaped microtubules and reduced aster formation, which however did not alter appreciably the rate of cell proliferation. Our findings establish that defective TBCD function underlies a recognizable encephalopathy and drives accelerated microtubule polymerization and enhanced microtubule stability, underscoring an additional cause of altered microtubule dynamics with impact on neuronal function and survival in the developing brain.
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http://dx.doi.org/10.1016/j.ajhg.2016.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5065658PMC
October 2016