Publications by authors named "Marjorie J Lindhurst"

20 Publications

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Ubiquitous expression of Akt1 p.(E17K) results in vascular defects and embryonic lethality in mice.

Hum Mol Genet 2020 Dec;29(20):3350-3360

Molecular Genomics and Metabolic Genetics Branch, NHGRI, NIH, Bethesda, MD 20892, USA.

Proteus syndrome is a progressive overgrowth disorder with vascular malformations caused by mosaic expression of the AKT1 c.49G > A, p.(E17K) activating variant which was predicted to cause lethality if expressed ubiquitously. To test that hypothesis, we used the ACTB-Cre gene to activate a conditional Akt1 p.(E17K) allele in the mouse. No offspring that was heterozygous for both Cre and the conditional allele (βA-Akt1WT/flx) was viable. Fewer than expected numbers of βA-Akt1WT/flx embryos were seen beginning at E11.5, but a few survived until E17.5. The phenotype ranged from mild to severe, but generally βA-Akt1WT/flx embryos had fewer visible blood vessels and more hemorrhages than their wild-type littermates, which was suggestive of a vascular abnormality. Examination of E13.5 limb skin showed a primitive capillary network with increased branching complexity and abnormal patterning compared with wild-type skin. By E15.5, wild-type skin had undergone angiogenesis and formed a hierarchical network of remodeled vessels, whereas in βA-Akt1WT/flx embryos, the capillary network failed to remodel. Mural cell coverage of the blood vessels was also reduced in βA-Akt1WT/flx skin compared with that of wild type. Restricting expression of Akt1E17K to endothelial, cardiac or smooth muscle cells resulted in viable offspring and remodeled vasculature and did not recapitulate the βA-Akt1WT/flx phenotype. We conclude that ubiquitous expression of Akt1E17K suppresses remodeling and inhibits the formation of a normal skin vasculature. We postulate that this failure prevents proper circulation necessary to support the growing embryo and that it is the result of interactions of multiple cell types with increased AKT signaling.
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http://dx.doi.org/10.1093/hmg/ddaa216DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7871364PMC
December 2020

Allelic heterogeneity of Proteus syndrome.

Cold Spring Harb Mol Case Stud 2020 06 12;6(3). Epub 2020 Jun 12.

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

Proteus syndrome is a mosaic disorder that can cause progressive postnatal overgrowth of nearly any organ or tissue. To date, Proteus syndrome has been exclusively associated with the mosaic c.49G > A p.(Glu17Lys) pathogenic variant in , a variant that is also present in many cancers. Here we describe an individual with severe Proteus syndrome who died at 7.5 yr of age from combined parenchymal and restrictive pulmonary disease. Remarkably, this individual was found to harbor a mosaic c.49_50delinsAG p.(Glu17Arg) variant in at a variant allele fraction that ranged from <0.01 to 0.46 in fibroblasts established from an overgrown digit. This variant was demonstrated to be constitutively activating by phosphorylation of AKT(S473). These data document allelic heterogeneity for Proteus syndrome. We recommend that individuals with a potential clinical diagnosis of Proteus syndrome who are negative for the p.(Glu17Lys) variant be tested for other variants in .
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http://dx.doi.org/10.1101/mcs.a005181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304363PMC
June 2020

Molecular heterogeneity of the cerebriform connective tissue nevus in mosaic overgrowth syndromes.

Cold Spring Harb Mol Case Stud 2019 08 1;5(4). Epub 2019 Aug 1.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.

The clinical diagnostic criteria for Proteus syndrome were defined before the discovery of the c.49G>A; p.(Glu17Lys) causal variant and used a combination of general and specific phenotypic attributes that could be combined to make a clinical diagnosis. The most heavily weighted specific criterion was the cerebriform connective tissue nevus (CCTN). Here, we describe two individuals with connective tissue nevi (CTNs) and some general attributes of Proteus syndrome who were found to have mosaic variants. CTNs on the soles of individuals with -related overgrowth typically exhibit thickening of the soft tissues with at most a wrinkled surface, but these two patients had firm plaques with ridges and furrows characteristic of CCTNs, which was histologically confirmed in one. These data show that CCTNs are not specific to Proteus syndrome and that clinicians should be cautious in diagnosing individuals with Proteus syndrome based on the CCTN alone. Rather, a complete evaluation should include careful assessment of other attributes of the diagnostic criteria and, whenever possible, genetic analysis of affected tissue.
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http://dx.doi.org/10.1101/mcs.a004036DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6672027PMC
August 2019

A mouse model of Proteus syndrome.

Hum Mol Genet 2019 09;28(17):2920-2936

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, MD, USA.

Proteus syndrome is a mosaic, progressive overgrowth disorder caused by a somatic activating variant c.49G > A p.(E17K) in AKT1. The presentation in affected individuals is variable, with a diversity of tissues demonstrating abnormalities. Common manifestations include skin and bony overgrowth, vascular malformations (VMs), cysts and benign tumors. We used two methods to create mouse models that had endogenously-regulated mosaic expression of the Proteus syndrome variant. Variant allele fractions (VAFs) ranged from 0% to 50% across numerous tissues in 44 Proteus syndrome mice. Mice were phenotypically heterogeneous with lesions rarely observed before 12 months of age. VMs were the most frequent finding with a total of 69 found in 29 of 44 Proteus syndrome mice. Twenty-eight cysts and ectasia, frequently biliary, were seen in 22 of 44 Proteus syndrome mice. Varying levels of mammary hyperplasia were seen in 10 of 16 female Proteus syndrome mice with other localized regions of hyperplasia and stromal expansion noted in several additional animals. Interestingly, 27 of 31 Proteus syndrome animals had non-zero blood VAF that is in contrast to the human disorder where it is rarely seen in peripheral blood. Identification of variant-positive cells by green fluorescent protein (GFP) staining in chimeric Proteus syndrome mice showed that in some lesions, hyperplastic cells were predominantly GFP/Akt1E17K-positive and showed increased pAKT signal compared to GFP-negative cells. However, hyperplastic mammary epithelium was a mixture of GFP/Akt1E17K-positive and negative cells with some GFP/Akt1E17K-negative cells also having increased pAKT signal suggesting that the variant-positive cells can induce lesion formation in a non-cell autonomous manner.
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http://dx.doi.org/10.1093/hmg/ddz116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6736390PMC
September 2019

Pharmacodynamic Study of Miransertib in Individuals with Proteus Syndrome.

Am J Hum Genet 2019 03 22;104(3):484-491. Epub 2019 Feb 22.

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, MD 20892, USA. Electronic address:

Proteus syndrome is a life-threatening segmental overgrowth syndrome caused by a mosaic gain-of-function AKT1 variant. There are no effective treatments for Proteus syndrome. Miransertib is an AKT1 inhibitor that, prior to this study, has been evaluated only in adult oncology trials. We designed a non-randomized, phase 0/1 pilot study of miransertib in adults and children with Proteus syndrome to identify an appropriate dosage starting point for a future efficacy trial using a pharmacodynamic endpoint. The primary endpoint was a 50% reduction in the tissue levels of AKT phosphorylation from biopsies in affected individuals. We also evaluated secondary efficacy endpoints. We found that a dose of 5 mg/m/day (1/7 the typical dose used in oncology) led to a 50% reduction in phosphorylated AKT (pAKT) in affected tissues from five of six individuals. This dose was well tolerated. Two of the six efficacy endpoints (secondary objectives) suggested that this agent may be efficacious. We observed a decrease in a cerebriform connective tissue nevus and a reduction in pain in children. We conclude that 5 mg/m/day of miransertib is an appropriate starting point for future efficacy trials and that this agent shows promise of therapeutic efficacy in children with Proteus syndrome.
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http://dx.doi.org/10.1016/j.ajhg.2019.01.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6407523PMC
March 2019

Safety and efficacy of low-dose sirolimus in the PIK3CA-related overgrowth spectrum.

Genet Med 2019 05 1;21(5):1189-1198. Epub 2018 Oct 1.

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.

Purpose: PIK3CA-related overgrowth spectrum (PROS) encompasses a range of debilitating conditions defined by asymmetric overgrowth caused by mosaic activating PIK3CA variants. PIK3CA encodes the p110α catalytic subunit of phosphatidylinositol-3-kinase (PI3K), a critical transducer of growth factor signaling. As mTOR mediates the growth-promoting actions of PI3K, we hypothesized that the mTOR inhibitor sirolimus would slow pathological overgrowth.

Methods: Thirty-nine participants with PROS and progressive overgrowth were enrolled into open-label studies across three centers, and results were pooled. For the primary outcome, tissue volumes at affected and unaffected sites were measured by dual energy X-ray absorptiometry during 26 weeks of untreated run-in and 26 weeks of sirolimus therapy.

Results: Thirty participants completed the study. Sirolimus led to a change in mean percentage total tissue volume of -7.2% (SD 16.0, p = 0.04) at affected sites, but not at unaffected sites (+1.7%, SD 11.5, p = 0.48) (n = 23 evaluable). Twenty-eight of 39 (72%) participants had ≥1 adverse event related to sirolimus of which 37% were grade 3 or 4 in severity and 7/39 (18%) participants were withdrawn consequently.

Conclusion: This study suggests that low-dose sirolimus can modestly reduce overgrowth, but cautions that the side-effect profile is significant, mandating individualized risk-benefit evaluations for sirolimus treatment in PROS.
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http://dx.doi.org/10.1038/s41436-018-0297-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752269PMC
May 2019

Mosaic RAS/MAPK variants cause sporadic vascular malformations which respond to targeted therapy.

J Clin Invest 2018 04 12;128(4):1496-1508. Epub 2018 Mar 12.

Genetics and Genomic Medicine, University College London (UCL) Great Ormond Street Institute of Child Health, London, United Kingdom.

Background: Sporadic vascular malformations (VMs) are complex congenital anomalies of blood vessels that lead to stroke, life-threatening bleeds, disfigurement, overgrowth, and/or pain. Therapeutic options are severely limited, and multidisciplinary management remains challenging, particularly for high-flow arteriovenous malformations (AVM).

Methods: To investigate the pathogenesis of sporadic intracranial and extracranial VMs in 160 children in which known genetic causes had been excluded, we sequenced DNA from affected tissue and optimized analysis for detection of low mutant allele frequency.

Results: We discovered multiple mosaic-activating variants in 4 genes of the RAS/MAPK pathway, KRAS, NRAS, BRAF, and MAP2K1, a pathway commonly activated in cancer and responsible for the germline RAS-opathies. These variants were more frequent in high-flow than low-flow VMs. In vitro characterization and 2 transgenic zebrafish AVM models that recapitulated the human phenotype validated the pathogenesis of the mutant alleles. Importantly, treatment of AVM-BRAF mutant zebrafish with the BRAF inhibitor vemurafinib restored blood flow in AVM.

Conclusion: Our findings uncover a major cause of sporadic VMs of different clinical types and thereby offer the potential of personalized medical treatment by repurposing existing licensed cancer therapies.

Funding: This work was funded or supported by grants from the AVM Butterfly Charity, the Wellcome Trust (UK), the Medical Research Council (UK), the UK National Institute for Health Research, the L'Oreal-Melanoma Research Alliance, the European Research Council, and the National Human Genome Research Institute (US).
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http://dx.doi.org/10.1172/JCI98589DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5873857PMC
April 2018

Pathogenetic insights from quantification of the cerebriform connective tissue nevus in Proteus syndrome.

J Am Acad Dermatol 2018 04 16;78(4):725-732. Epub 2017 Oct 16.

Department of Dermatology, Uniformed Services University of the Health Sciences, Bethesda, Maryland. Electronic address:

Background: The plantar cerebriform connective tissue nevus (CCTN) is the most common and problematic cutaneous manifestation of Proteus syndrome.

Objective: To gain insights into CCTN pathogenesis and natural history.

Methods: The size and location of plantar CCTN was measured on 152 images from 22 individuals with Proteus syndrome by 2 independent, blinded reviewers. Average measures of plantar CCTN were transformed into a linear mixed model to estimate proportionate change in size with age.

Results: Median patient age was 6.9 years at study onset. The intraclass correlation coefficient between 2 blinded reviewers was 0.946 for CCTN single measures. The CCTN relative area increased with age in children (n = 18, P < .0001) by 5.6% per year. Confluent papules and nodules extending beyond the boundaries of CCTNs were gradually replaced by typical CCTN over time. The location of CCTN in different individuals overlapped near the ball of the foot. A positive relationship between CCTN growth rate and AKT1 mutant allele frequency was observed (0.62, P = .10, n = 8).

Limitations: This was a retrospective review using photographs.

Conclusion: CCTN growth is affected by age and extent of the CCTN precursor lesion. Monitoring of CCTN size might prove useful for evaluating drug response in the treatment of Proteus syndrome.
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http://dx.doi.org/10.1016/j.jaad.2017.10.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5857242PMC
April 2018

Somatic AKT1 mutations cause meningiomas colocalizing with a characteristic pattern of cranial hyperostosis.

Am J Med Genet A 2016 10 23;170(10):2605-10. Epub 2016 Aug 23.

Medical Genomics and Metabolic Genetics Branch, National Human Genetics Research Branch, National Institutes of Health, Bethesda, Maryland.

Somatic genetic mutations in meningiomas are associated with histologic subtypes, anatomical location, and grade. Concomitant hyperostosis occurs with some meningiomas and the pathogenesis is not well understood. Cranial hyperostosis and meningiomas are common in patients with Proteus syndrome, which is caused by a somatic activating mutation in AKT1 c.49G>A. This same mutation has also been found in 6-9% of sporadic non-syndromic meningiomas. Sixty-one patients with Proteus syndrome meeting clinical diagnostic criteria were evaluated at the NIH from 1997 to 2014. Of these 61, 52 had a somatic activating mutation (c.49G>A, p.Glu17Lys) in AKT1 confirmed from affected tissue samples. Photographs, physical examination and/or autopsy, X-rays, CT, and/or MRI scan of the head were reviewed in 29/52 patients. Of the 29 patients, the most common intracranial tumor was meningioma, all co-localizing with cranial hyperostosis, and diagnosed at younger ages than typical for isolated, non-syndromic meningiomas. These patients had progressive cranial overgrowth that consisted primarily of diploic space expansion, and was characterized by unilateral, parasagittal, and frontal bone involvement. We hypothesize that sporadic meningothelial and transitional subtype meningiomas are a forme fruste or microform of Proteus syndrome, and activation of the AKT/PI3K pathway drives hyperostosis in both non-syndromic, and Proteus-related meningiomas. © 2016 The Authors. American Journal of Medical Genetics Part A Published by Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37737DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5580816PMC
October 2016

Lack of mutation-histopathology correlation in a patient with Proteus syndrome.

Am J Med Genet A 2016 06 26;170(6):1422-1432. Epub 2016 Apr 26.

Medical Genomics and Metabolic Genetics Branch, National Human Genome Research Institute, Bethesda, Maryland.

Proteus syndrome (PS) is characterized by progressive, disproportionate, segmental overgrowth, and tumor susceptibility caused by a somatic mosaic AKT1 activating mutation. Each individual has unique manifestations making this disorder extremely heterogeneous. We correlated three variables in 38 tissue samples from a patient who died with PS: the gross affection status, the microscopic affection status, and the mutation level. The AKT1 mutation was measured using a PCR-based RFLP assay. Thirteen samples were grossly normal; six had detectable mutation (2-29%) although four of these six were histopathologically normal. Of the seven grossly normal samples that had no mutation, only four were histologically normal. The mutation level in the grossly abnormal samples was 3-35% and all but the right and left kidneys, skull, and left knee bone, with mutation levels of 19%, 15%, 26%, and 17%, respectively, had abnormal histopathology. The highest mutation level was in a toe bone sample whereas the lowest levels were in the soft tissue surrounding that toe, and an omental fat nodule. We also show here that PS overgrowth can be caused by cellular proliferation or by extracellular matrix expansion. Additionally, papillary thyroid carcinoma was identified, a tumor not previously associated with PS. We conclude that gross pathology and histopathology correlate poorly with mutation levels in PS, that overgrowth can be mediated by cellular proliferation or extracellular matrix expansion, and that papillary thyroid carcinoma is part of the tumor susceptibility of PS. New methods need to be developed to facilitate genotype-phenotype correlation in mosaic disorders. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37612DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5042707PMC
June 2016

Mosaic Activating Mutations in FGFR1 Cause Encephalocraniocutaneous Lipomatosis.

Am J Hum Genet 2016 Mar;98(3):579-587

Children's Hospital of Eastern Ontario Research Institute, University of Ottawa, Ottawa, ON K1H5B2, Canada.

Encephalocraniocutaneous lipomatosis (ECCL) is a sporadic condition characterized by ocular, cutaneous, and central nervous system anomalies. Key clinical features include a well-demarcated hairless fatty nevus on the scalp, benign ocular tumors, and central nervous system lipomas. Seizures, spasticity, and intellectual disability can be present, although affected individuals without seizures and with normal intellect have also been reported. Given the patchy and asymmetric nature of the malformations, ECCL has been hypothesized to be due to a post-zygotic, mosaic mutation. Despite phenotypic overlap with several other disorders associated with mutations in the RAS-MAPK and PI3K-AKT pathways, the molecular etiology of ECCL remains unknown. Using exome sequencing of DNA from multiple affected tissues from five unrelated individuals with ECCL, we identified two mosaic mutations, c.1638C>A (p.Asn546Lys) and c.1966A>G (p.Lys656Glu) within the tyrosine kinase domain of FGFR1, in two affected individuals each. These two residues are the most commonly mutated residues in FGFR1 in human cancers and are associated primarily with CNS tumors. Targeted resequencing of FGFR1 in multiple tissues from an independent cohort of individuals with ECCL identified one additional individual with a c.1638C>A (p.Asn546Lys) mutation in FGFR1. Functional studies of ECCL fibroblast cell lines show increased levels of phosphorylated FGFRs and phosphorylated FRS2, a direct substrate of FGFR1, as well as constitutive activation of RAS-MAPK signaling. In addition to identifying the molecular etiology of ECCL, our results support the emerging overlap between mosaic developmental disorders and tumorigenesis.
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http://dx.doi.org/10.1016/j.ajhg.2016.02.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4800051PMC
March 2016

Repression of AKT signaling by ARQ 092 in cells and tissues from patients with Proteus syndrome.

Sci Rep 2015 Dec 11;5:17162. Epub 2015 Dec 11.

National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.

A somatic activating mutation in AKT1, c.49G>A, pGlu17Lys, that results in elevated AKT signaling in mutation-positive cells, is responsible for the mosaic overgrowth condition, Proteus syndrome. ARQ 092 is an allosteric pan-AKT inhibitor under development for treatment in cancer. We tested the efficacy of this drug for suppressing AKT signaling in cells and tissues from patients with Proteus syndrome. ARQ 092 reduced phosphorylation of AKT and downstream targets of AKT in a concentration-dependent manner in as little as two hours. While AKT signaling was suppressed with ARQ 092 treatment, cells retained their ability to respond to growth factor stimulation by increasing pAKT levels proportionally to untreated cells. At concentrations sufficient to decrease AKT signaling, little reduction in cell viability was seen. These results indicate that ARQ 092 can suppress AKT signaling and warrants further development as a therapeutic option for patients with Proteus syndrome.
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http://dx.doi.org/10.1038/srep17162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4675973PMC
December 2015

PIK3CA-related overgrowth spectrum (PROS): diagnostic and testing eligibility criteria, differential diagnosis, and evaluation.

Am J Med Genet A 2015 Feb 31;167A(2):287-95. Epub 2014 Dec 31.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland.

Somatic activating mutations in the phosphatidylinositol-3-kinase/AKT/mTOR pathway underlie heterogeneous segmental overgrowth phenotypes. Because of the extreme differences among patients, we sought to characterize the phenotypic spectrum associated with different genotypes and mutation burdens, including a better understanding of associated complications and natural history. Historically, the clinical diagnoses in patients with PIK3CA activating mutations have included Fibroadipose hyperplasia or Overgrowth (FAO), Hemihyperplasia Multiple Lipomatosis (HHML), Congenital Lipomatous Overgrowth, Vascular Malformations, Epidermal Nevi, Scoliosis/Skeletal and Spinal (CLOVES) syndrome, macrodactyly, Fibroadipose Infiltrating Lipomatosis, and the related megalencephaly syndromes, Megalencephaly-Capillary Malformation (MCAP or M-CM) and Dysplastic Megalencephaly (DMEG). A workshop was convened at the National Institutes of Health (NIH) to discuss and develop a consensus document regarding diagnosis and treatment of patients with PIK3CA-associated somatic overgrowth disorders. Participants in the workshop included a group of researchers from several institutions who have been studying these disorders and have published their findings, as well as representatives from patient-advocacy and support groups. The umbrella term of "PIK3CA-Related Overgrowth Spectrum (PROS)" was agreed upon to encompass both the known and emerging clinical entities associated with somatic PIK3CA mutations including, macrodactyly, FAO, HHML, CLOVES, and related megalencephaly conditions. Key clinical diagnostic features and criteria for testing were proposed, and testing approaches summarized. Preliminary recommendations for a uniform approach to assessment of overgrowth and molecular diagnostic testing were determined. Future areas to address include the surgical management of overgrowth tissue and vascular anomalies, the optimal approach to thrombosis risk, and the testing of potential pharmacologic therapies.
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http://dx.doi.org/10.1002/ajmg.a.36836DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4480633PMC
February 2015

A limited form of proteus syndrome with bilateral plantar cerebriform collagenomas and varicose veins secondary to a mosaic AKT1 mutation.

JAMA Dermatol 2014 Sep;150(9):990-3

Department of Dermatology, St Helier University Hospital, Surrey, England.

Importance: Proteus syndrome is an extremely rare disorder of mosaic postnatal overgrowth affecting multiple tissues including bone, soft tissue, and skin. It typically manifests in early childhood with asymmetric and progressive skeletal overgrowth that leads to severe distortion of the skeleton and disability. The genetic basis has recently been identified as a somatic activating mutation in the AKT1 gene, which encodes an enzyme mediating cell proliferation and apoptosis.

Observations: We present a 33-year-old man who developed plantar cerebriform collagenomas on the soles of both feet and varicose veins in early childhood, in the absence of any skeletal or other connective tissue abnormality. Although the patient did not meet the diagnostic criteria for Proteus syndrome, he was found to have the c.49G>A, p.Glu17Lys AKT1 mutation in lesional skin but not in his blood.

Conclusions And Relevance: To our knowledge, this is the mildest molecularly confirmed case of Proteus syndrome, occurring in the absence of the characteristic skeletal overgrowth. These findings extend the spectrum of Proteus syndrome pathological characteristics and suggest that somatic mutations late in development and restricted in distribution cause subtle clinical presentations that do not meet the published clinical criteria.
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http://dx.doi.org/10.1001/jamadermatol.2013.10368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4281031PMC
September 2014

Clinical delineation and natural history of the PIK3CA-related overgrowth spectrum.

Am J Med Genet A 2014 Jul 29;164A(7):1713-33. Epub 2014 Apr 29.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland.

Somatic mutations in the phosphatidylinositol/AKT/mTOR pathway cause segmental overgrowth disorders. Diagnostic descriptors associated with PIK3CA mutations include fibroadipose overgrowth (FAO), Hemihyperplasia multiple Lipomatosis (HHML), Congenital Lipomatous Overgrowth, Vascular malformations, Epidermal nevi, Scoliosis/skeletal and spinal (CLOVES) syndrome, macrodactyly, and the megalencephaly syndrome, Megalencephaly-Capillary malformation (MCAP) syndrome. We set out to refine the understanding of the clinical spectrum and natural history of these phenotypes, and now describe 35 patients with segmental overgrowth and somatic PIK3CA mutations. The phenotypic data show that these previously described disease entities have considerable overlap, and represent a spectrum. While this spectrum overlaps with Proteus syndrome (sporadic, mosaic, and progressive) it can be distinguished by the absence of cerebriform connective tissue nevi and a distinct natural history. Vascular malformations were found in 15/35 (43%) and epidermal nevi in 4/35 (11%) patients, lower than in Proteus syndrome. Unlike Proteus syndrome, 31/35 (89%) patients with PIK3CA mutations had congenital overgrowth, and in 35/35 patients this was asymmetric and disproportionate. Overgrowth was mild with little postnatal progression in most, while in others it was severe and progressive requiring multiple surgeries. Novel findings include: adipose dysregulation present in all patients, unilateral overgrowth that is predominantly left-sided, overgrowth that affects the lower extremities more than the upper extremities and progresses in a distal to proximal pattern, and in the most severely affected patients is associated with marked paucity of adipose tissue in unaffected areas. While the current data are consistent with some genotype-phenotype correlation, this cannot yet be confirmed.
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http://dx.doi.org/10.1002/ajmg.a.36552DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4320693PMC
July 2014

AKT1 gene mutation levels are correlated with the type of dermatologic lesions in patients with Proteus syndrome.

J Invest Dermatol 2014 Feb 24;134(2):543-546. Epub 2013 Jul 24.

National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA.

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http://dx.doi.org/10.1038/jid.2013.312DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3868633PMC
February 2014

Mosaic overgrowth with fibroadipose hyperplasia is caused by somatic activating mutations in PIK3CA.

Nat Genet 2012 Jun 24;44(8):928-33. Epub 2012 Jun 24.

The National Human Genome Research Institute, US National Institutes of Health, Bethesda, Maryland, USA.

The phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway is critical for cellular growth and metabolism. Correspondingly, loss of function of PTEN, a negative regulator of PI3K, or activating mutations in AKT1, AKT2 or AKT3 have been found in distinct disorders featuring overgrowth or hypoglycemia. We performed exome sequencing of DNA from unaffected and affected cells from an individual with an unclassified syndrome of congenital progressive segmental overgrowth of fibrous and adipose tissue and bone and identified the cancer-associated mutation encoding p.His1047Leu in PIK3CA, the gene that encodes the p110α catalytic subunit of PI3K, only in affected cells. Sequencing of PIK3CA in ten additional individuals with overlapping syndromes identified either the p.His1047Leu alteration or a second cancer-associated alteration, p.His1047Arg, in nine cases. Affected dermal fibroblasts showed enhanced basal and epidermal growth factor (EGF)-stimulated phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) generation and concomitant activation of downstream signaling relative to their unaffected counterparts. Our findings characterize a distinct overgrowth syndrome, biochemically demonstrate activation of PI3K signaling and thereby identify a rational therapeutic target.
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http://dx.doi.org/10.1038/ng.2332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3461408PMC
June 2012

A mosaic activating mutation in AKT1 associated with the Proteus syndrome.

N Engl J Med 2011 Aug 27;365(7):611-9. Epub 2011 Jul 27.

National Human Genome Research Institute, Bethesda, Maryland, USA.

Background: The Proteus syndrome is characterized by the overgrowth of skin, connective tissue, brain, and other tissues. It has been hypothesized that the syndrome is caused by somatic mosaicism for a mutation that is lethal in the nonmosaic state.

Methods: We performed exome sequencing of DNA from biopsy samples obtained from patients with the Proteus syndrome and compared the resultant DNA sequences with those of unaffected tissues obtained from the same patients. We confirmed and extended an observed association, using a custom restriction-enzyme assay to analyze the DNA in 158 samples from 29 patients with the Proteus syndrome. We then assayed activation of the AKT protein in affected tissues, using phosphorylation-specific antibodies on Western blots.

Results: Of 29 patients with the Proteus syndrome, 26 had a somatic activating mutation (c.49G→A, p.Glu17Lys) in the oncogene AKT1, encoding the AKT1 kinase, an enzyme known to mediate processes such as cell proliferation and apoptosis. Tissues and cell lines from patients with the Proteus syndrome harbored admixtures of mutant alleles that ranged from 1% to approximately 50%. Mutant cell lines showed greater AKT phosphorylation than did control cell lines. A pair of single-cell clones that were established from the same starting culture and differed with respect to their mutation status had different levels of AKT phosphorylation.

Conclusions: The Proteus syndrome is caused by a somatic activating mutation in AKT1, proving the hypothesis of somatic mosaicism and implicating activation of the PI3K-AKT pathway in the characteristic clinical findings of overgrowth and tumor susceptibility in this disorder. (Funded by the Intramural Research Program of the National Human Genome Research Institute.).
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http://dx.doi.org/10.1056/NEJMoa1104017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3170413PMC
August 2011

Knockout of Slc25a19 causes mitochondrial thiamine pyrophosphate depletion, embryonic lethality, CNS malformations, and anemia.

Proc Natl Acad Sci U S A 2006 Oct 11;103(43):15927-32. Epub 2006 Oct 11.

National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA.

SLC25A19 mutations cause Amish lethal microcephaly (MCPHA), which markedly retards brain development and leads to alpha-ketoglutaric aciduria. Previous data suggested that SLC25A19, also called DNC, is a mitochondrial deoxyribonucleotide transporter. We generated a knockout mouse model of Slc25a19. These animals had 100% prenatal lethality by embryonic day 12. Affected embryos at embryonic day 10.5 have a neural-tube closure defect with ruffling of the neural fold ridges, a yolk sac erythropoietic failure, and elevated alpha-ketoglutarate in the amniotic fluid. We found that these animals have normal mitochondrial ribo- and deoxyribonucleoside triphosphate levels, suggesting that transport of these molecules is not the primary role of SLC25A19. We identified thiamine pyrophosphate (ThPP) transport as a candidate function of SLC25A19 through homology searching and confirmed it by using transport assays of the recombinant reconstituted protein. The mitochondria of Slc25a19(-/-) and MCPHA cells have undetectable and markedly reduced ThPP content, respectively. The reduction of ThPP levels causes dysfunction of the alpha-ketoglutarate dehydrogenase complex, which explains the high levels of this organic acid in MCPHA and suggests that mitochondrial ThPP transport is important for CNS development.
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http://dx.doi.org/10.1073/pnas.0607661103DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1595310PMC
October 2006