The expanding clinical and genetic spectrum of DYNC1H1-related disorders.

Intracellular trafficking involves an intricate machinery of motor complexes including the dynein complex to shuttle cargo for autophagolysosomal degradation. Deficiency in dynein axonemal chains as well as cytoplasmic light and intermediate chains have been linked with ciliary dyskinesia and skeletal dysplasia. The cytoplasmic dynein 1 heavy chain protein (DYNC1H1) serves as a core complex for retrograde trafficking in neuronal axons. Dominant pathogenic variants in DYNC1H1 have been previously implicated in peripheral neuromuscular disorders (NMD) and neurodevelopmental disorders (NDD). As heavy-chain dynein is ubiquitously expressed, the apparent selectivity of heavy-chain dyneinopathy for motor neuronal phenotypes remains currently unaccounted for. Here, we aimed to evaluate the full DYNC1H1-related clinical, molecular and imaging spectrum, including multisystem features and novel phenotypes presenting throughout life. We identified 47 cases from 43 families with pathogenic heterozygous variants in DYNC1H1 (aged 0-59 years) and collected phenotypic data via a comprehensive standardized survey and clinical follow-up appointments. Most patients presented with divergent and previously unrecognized neurological and multisystem features, leading to significant delays in genetic testing and establishing the correct diagnosis. Neurological phenotypes include novel autonomic features, previously rarely described behavioral disorders, movement disorders, and periventricular lesions. Sensory neuropathy was identified in nine patients (median age of onset 10.6 years), of which five were only diagnosed after the second decade of life, and three had a progressive age-dependent sensory neuropathy. Novel multisystem features included primary immunodeficiency, bilateral sensorineural hearing loss, organ anomalies, and skeletal manifestations, resembling the phenotypic spectrum of other dyneinopathies. We also identified an age-dependent biphasic disease course with developmental regression in the first decade and, following a period of stability, neurodegenerative progression after the second decade of life. Of note, we observed several cases in whom neurodegeneration appeared to be prompted by intercurrent systemic infections with double-stranded DNA viruses (Herpesviridae) or single-stranded RNA viruses (Ross-River fever, SARS-CoV-2). Moreover, the disease course appeared to be exacerbated by viral infections regardless of age and/or severity of NDD manifestations, indicating a role of dynein in anti-viral immunity and neuronal health. In summary, our findings expand the clinical, imaging, and molecular spectrum of pathogenic DYNC1H1 variants beyond motor neuropathy disorders and suggest a life-long continuum and age-related progression due to deficient intracellular trafficking. This study will facilitate early diagnosis and improve counselling and health surveillance of affected patients.

Extending the clinical spectrum of X-linked Tonne-Kalscheuer syndrome (TOKAS): new insights from the fetal perspective.

INTRODUCTION: Tonne-Kalscheuer syndrome (TOKAS) is a recessive X-linked multiple congenital anomaly disorder caused by RLIM variations. Of the 41 patients reported, only 7 antenatal cases were described. METHOD: After the antenatal diagnosis of TOKAS by exome analysis in a family followed for over 35 years because of multiple congenital anomalies in five male fetuses, a call for collaboration was made, resulting in a cohort of 11 previously unpublished cases. RESULTS: We present a TOKAS antenatal cohort, describing 11 new cases in 6 French families. We report a high frequency of diaphragmatic hernia (9 of 11), differences in sex development (10 of 11) and various visceral malformations. We report some recurrent dysmorphic features, but also pontocerebellar hypoplasia, pre-auricular skin tags and olfactory bulb abnormalities previously unreported in the literature. Although no clear genotype-phenotype correlation has yet emerged, we show that a recurrent p.(Arg611Cys) variant accounts for 66% of fetal TOKAS cases. We also report two new likely pathogenic variants in RLIM, outside of the two previously known mutational hotspots. CONCLUSION: Overall, we present the first fetal cohort of TOKAS, describe the clinical features that made it a recognisable syndrome at fetopathological examination, and extend the phenotypical spectrum and the known genotype of this rare disorder.

Haploinsufficiency of the Sin3/HDAC corepressor complex member SIN3B causes a syndromic intellectual disability/autism spectrum disorder.

Proteins involved in transcriptional regulation harbor a demonstrated enrichment of mutations in neurodevelopmental disorders. The Sin3 (Swi-independent 3)/histone deacetylase (HDAC) complex plays a central role in histone deacetylation and transcriptional repression. Among the two vertebrate paralogs encoding the Sin3 complex, SIN3A variants cause syndromic intellectual disability, but the clinical consequences of SIN3B haploinsufficiency in humans are uncharacterized. Here, we describe a syndrome hallmarked by intellectual disability, developmental delay, and dysmorphic facial features with variably penetrant autism spectrum disorder, congenital malformations, corpus callosum defects, and impaired growth caused by disruptive SIN3B variants. Using chromosomal microarray or exome sequencing, and through international data sharing efforts, we identified nine individuals with heterozygous SIN3B deletion or single-nucleotide variants. Five individuals harbor heterozygous deletions encompassing SIN3B that reside within a ∼230 kb minimal region of overlap on 19p13.11, two individuals have a rare nonsynonymous substitution, and two individuals have a single-nucleotide deletion that results in a frameshift and predicted premature termination codon. To test the relevance of SIN3B impairment to measurable aspects of the human phenotype, we disrupted the orthologous zebrafish locus by genome editing and transient suppression. The mutant and morphant larvae display altered craniofacial patterning, commissural axon defects, and reduced body length supportive of an essential role for Sin3 function in growth and patterning of anterior structures. To investigate further the molecular consequences of SIN3B variants, we quantified genome-wide enhancer and promoter activity states by using H3K27ac ChIP-seq. We show that, similar to SIN3A mutations, SIN3B disruption causes hyperacetylation of a subset of enhancers and promoters in peripheral blood mononuclear cells. Together, these data demonstrate that SIN3B haploinsufficiency leads to a hitherto unknown intellectual disability/autism syndrome, uncover a crucial role of SIN3B in the central nervous system, and define the epigenetic landscape associated with Sin3 complex impairment.

Cerebral dural arteriovenous fistulas in patients with PTEN-related hamartoma tumor syndrome.

Central nervous system (CNS) dural arteriovenous fistulas (DAVF) have been reported in PTEN-related hamartoma tumor syndrome (PHTS). However, PHTS-associated DAVF remain an underexplored field of the PHTS clinical landscape. Here, we studied cases with a PTEN pathogenic variant identified between 2007 and 2020 in our laboratory (n = 58), and for whom brain imaging was available. Two patients had DAVF (2/58, 3.4%), both presenting at advanced stages: a 34-year-old man with a left lateral sinus DAVF at immediate risk of hemorrhage, and a 21-year-old woman with acute intracranial hypertension due to a torcular DAVF. Interestingly, not all patients had 3D TOF/MRA, the optimal sequences to detect DAVF. Early diagnosis of DAVF can be lifesaving, and is easier to treat compared to developed, proliferative, or complex lesions. As a result, one should consider brain MRI with 3D TOF/MRA in PHTS patients at genetic diagnosis, with subsequent surveillance on a case-by-case basis.

Variants in CLDN5 cause a syndrome characterized by seizures, microcephaly and brain calcifications.

The blood-brain barrier ensures CNS homeostasis and protection from injury. Claudin-5 (CLDN5), an important component of tight junctions, is critical for the integrity of the blood-brain barrier. We have identified de novo heterozygous missense variants in CLDN5 in 15 unrelated patients who presented with a shared constellation of features including developmental delay, seizures (primarily infantile onset focal epilepsy), microcephaly and a recognizable pattern of pontine atrophy and brain calcifications. All variants clustered in one subregion/domain of the CLDN5 gene and the recurrent variants demonstrate genotype-phenotype correlations. We modelled both patient variants and loss of function alleles in the zebrafish to show that the variants analogous to those in patients probably result in a novel aberrant function in CLDN5. In total, human patient and zebrafish data provide parallel evidence that pathogenic sequence variants in CLDN5 cause a novel neurodevelopmental disorder involving disruption of the blood-brain barrier and impaired neuronal function.

Biallelic NPR1 loss of function variants are responsible for neonatal systemic hypertension.

BACKGROUND: Early-onset isolated systemic hypertension is a rare condition of unknown genetic origin. Renovascular, renal parenchymal diseases or aortic coarctation are the most common causes of secondary systemic hypertension in younger children and neonates. We investigated the genetic bases of early-onset isolated systemic hypertension. METHODS: Whole-exome sequencing (WES) was followed by variant filtering and Sanger sequencing for validation and familial segregation of selected variants in a large consanguineous family. mRNA expression was performed to evaluate the impact of the predicted pathogenic variant on gene expression. WES or Sanger sequencing was performed in additional unrelated affected individuals. RESULTS: In one consanguineous family with four children presenting with isolated neonatal-onset systemic hypertension, we identified homozygous stop-gain variant in the NPR1 gene (NM_000906.4:c.1159C>T (p.Arg387Ter)) in the affected individuals. This variant leads to a dramatic reduction of NPR1 RNA levels. NPR1 gene analysis of additional families allowed the identification of another family with two affected children carrying homozygous frameshift variant in NPR1 (NM_000906.4:c.175del (p.Val59TrpfsTer8)). CONCLUSION: We show for the first time that biallelic loss of function of NPR1 is responsible for isolated neonatal-onset systemic hypertension in humans, which represents a new autosomal recessive genetic cause of infantile systemic hypertension or cardiogenic shock. This is consistent with studies reporting early-onset systemic hypertension and sudden death in Npr1-deficient mice. NPR1 gene analysis should be therefore investigated in infants with early-onset systemic hypertension with or without cardiogenic shock of unknown origin.

Dermatological manifestations in Costello syndrome: A prospective multicentric study of 31 HRAS-positive variant patients.

BACKGROUND: Data on dermatological manifestations of Costello syndrome (CS) remain heterogeneous and lack in validated description. OBJECTIVES: To describe the dermatological manifestations of CS; compare them with the literature findings; assess those discriminating CS from other RASopathies, including cardiofaciocutaneous syndrome (CFCS) and the main types of Noonan syndrome (NS); and test for dermatological phenotype-genotype correlations. METHODS: We performed a 10-year, large, prospective, multicentric, collaborative dermatological and genetic study. RESULTS: Thirty-one patients were enrolled. Hair abnormalities were ubiquitous, including wavy or curly hair and excessive eyebrows, respectively in 68% and 56%. Acral excessive skin (AES), papillomas and keratotic papules (PKP), acanthosis nigricans (AN), palmoplantar hyperkeratosis (PPHK) and 'cobblestone' papillomatous papules of the upper lip (CPPUL), were noted respectively in 84%, 61%, 65%, 55% and 32%. Excessive eyebrows, PKP, AN, CCPUL and AES best differentiated CS from CFCS and NS. Multiple melanocytic naevi (>50) may constitute a new marker of attenuated CS associated with intragenic duplication in HRAS. Oral acitretin may be highly beneficial for therapeutic management of PPHK. No significant dermatological phenotype-genotype correlation was determined between patients with and without HRAS c.34G>A (p.G12S). CONCLUSIONS AND RELEVANCE: This validated phenotypic characterization of a large number of patients with CS will allow future researchers to make a positive diagnosis, and to differentiate CS from CFCS and NS.

Mutations in MYLPF Cause a Novel Segmental Amyoplasia that Manifests as Distal Arthrogryposis.

We identified ten persons in six consanguineous families with distal arthrogryposis (DA) who had congenital contractures, scoliosis, and short stature. Exome sequencing revealed that each affected person was homozygous for one of two different rare variants (c.470G>T [p.Cys157Phe] or c.469T>C [p.Cys157Arg]) affecting the same residue of myosin light chain, phosphorylatable, fast skeletal muscle (MYLPF). In a seventh family, a c.487G>A (p.Gly163Ser) variant in MYLPF arose de novo in a father, who transmitted it to his son. In an eighth family comprised of seven individuals with dominantly inherited DA, a c.98C>T (p.Ala33Val) variant segregated in all four persons tested. Variants in MYLPF underlie both dominant and recessively inherited DA. Mylpf protein models suggest that the residues associated with dominant DA interact with myosin whereas the residues altered in families with recessive DA only indirectly impair this interaction. Pathological and histological exam of a foot amputated from an affected child revealed complete absence of skeletal muscle (i.e., segmental amyoplasia). To investigate the mechanism for this finding, we generated an animal model for partial MYLPF impairment by knocking out zebrafish mylpfa. The mylpfa mutant had reduced trunk contractile force and complete pectoral fin paralysis, demonstrating that mylpf impairment most severely affects limb movement. mylpfa mutant muscle weakness was most pronounced in an appendicular muscle and was explained by reduced myosin activity and fiber degeneration. Collectively, our findings demonstrate that partial loss of MYLPF function can lead to congenital contractures, likely as a result of degeneration of skeletal muscle in the distal limb.

Opposite Modulation of RAC1 by Mutations in TRIO Is Associated with Distinct, Domain-Specific Neurodevelopmental Disorders.

The Rho-guanine nucleotide exchange factor (RhoGEF) TRIO acts as a key regulator of neuronal migration, axonal outgrowth, axon guidance, and synaptogenesis by activating the GTPase RAC1 and modulating actin cytoskeleton remodeling. Pathogenic variants in TRIO are associated with neurodevelopmental diseases, including intellectual disability (ID) and autism spectrum disorders (ASD). Here, we report the largest international cohort of 24 individuals with confirmed pathogenic missense or nonsense variants in TRIO. The nonsense mutations are spread along the TRIO sequence, and affected individuals show variable neurodevelopmental phenotypes. In contrast, missense variants cluster into two mutational hotspots in the TRIO sequence, one in the seventh spectrin repeat and one in the RAC1-activating GEFD1. Although all individuals in this cohort present with developmental delay and a neuro-behavioral phenotype, individuals with a pathogenic variant in the seventh spectrin repeat have a more severe ID associated with macrocephaly than do most individuals with GEFD1 variants, who display milder ID and microcephaly. Functional studies show that the spectrin and GEFD1 variants cause a TRIO-mediated hyper- or hypo-activation of RAC1, respectively, and we observe a striking correlation between RAC1 activation levels and the head size of the affected individuals. In addition, truncations in TRIO GEFD1 in the vertebrate model X. tropicalis induce defects that are concordant with the human phenotype. This work demonstrates distinct clinical and molecular disorders clustering in the GEFD1 and seventh spectrin repeat domains and highlights the importance of tight control of TRIO-RAC1 signaling in neuronal development.

DST variants are responsible for neurogenic arthrogryposis multiplex congenita enlarging the spectrum of type VI hereditary sensory autonomic neuropathy.

Arthrogryposis multiplex congenita (AMC) is a developmental condition characterized by multiple joint contractures resulting from reduced or absent fetal movements. Through whole-exome sequencing combined with arrayCGH from DNA of a fetus presenting with early onset AMC, we identified biallelic loss of function variants in Dystonin (DST): a stop gain variant (NM_001144769.5:c.12208G > T:p.(Glu4070Ter)) on the neuronal isoform and a 175 kb microdeletion including exons 25-96 of this isoform on the other allele [NC_000006.11:g.(56212278_56323554)_(56499398_56507586)del]. Transmission electron microscopy of the sciatic nerve revealed abnormal morphology of the peripheral nerve with severe hypomyelination associated with dramatic reduction of fiber density which highlights the critical role of DST in peripheral nerve axonogenesis during development in human. Variants in the neuronal isoforms of DST cause hereditary sensory and autonomic neuropathy which has been reported in several unrelated families with highly variable age of onset from fetal to adult onset. Our data enlarge the disease mechanisms of neurogenic AMC.

Germline bi-allelic SH2B3/LNK alteration predisposes to a neonatal juvenile myelomonocytic leukemia-like disorder.

Juvenile myelomonocytic leukemia (JMML) is a rare, generally aggressive myeloproliferative neoplasm affecting young children. It is characterized by granulomonocytic expansion, with monocytosis infiltrating peripheral tissues. JMML is initiated by mutations upregulating RAS signaling. Approximately 10% of cases remain without an identified driver event. Exome sequencing of 2 unrelated cases of familial JMML of unknown genetics and analysis of the French JMML cohort identified 11 patients with variants in SH2B3, encoding LNK, a negative regulator of the JAK-STAT pathway. All variants were absent from healthy population databases, and mutation spectrum was consistent with a loss of function of the LNK protein. A stoploss variant was shown to affect both protein synthesis and stability. The other variants were either truncating or missense, the latter affecting the SH2 domain that interacts with activated JAK. Of the 11 patients, 8 from 5 families inherited pathogenic bi-allelic SH2B3 germline variants from their unaffected heterozygous parents. These children represent half of the cases with no identified causal mutation in the French cohort. They displayed typical clinical and hematological JMML features with neonatal onset and marked thrombocytopenia. They were characterized by absence of additional genetic alterations and a hypomethylated DNA profile with fetal characteristics. All patients showed partial or complete spontaneous clinical resolution. However, progression to thrombocythemia and immunity-related pathologies may be of concern later in life. Bi-allelic SH2B3 germline mutations thus define a new condition predisposing to a JMML-like disorder, suggesting that the JAK pathway deregulation is capable of initiating JMML, and opening new therapeutic options.

Phenotypic spectrum and genomics of undiagnosed arthrogryposis multiplex congenita.

BACKGROUND: Arthrogryposis multiplex congenita (AMC) is characterised by congenital joint contractures in two or more body areas. AMC exhibits wide phenotypic and genetic heterogeneity. Our goals were to improve the genetic diagnosis rates of AMC, to evaluate the added value of whole exome sequencing (WES) compared with targeted exome sequencing (TES) and to identify new genes in 315 unrelated undiagnosed AMC families. METHODS: Several genomic approaches were used including genetic mapping of disease loci in multiplex or consanguineous families, TES then WES. Sanger sequencing was performed to identify or validate variants. RESULTS: We achieved disease gene identification in 52.7% of AMC index patients including nine recently identified genes (CNTNAP1, MAGEL2, ADGRG6, ADCY6, GLDN, LGI4, LMOD3, UNC50 and SCN1A). Moreover, we identified pathogenic variants in ASXL3 and STAC3 expanding the phenotypes associated with these genes. The most frequent cause of AMC was a primary involvement of skeletal muscle (40%) followed by brain (22%). The most frequent mode of inheritance is autosomal recessive (66.3% of patients). In sporadic patients born to non-consanguineous parents (n=60), de novo dominant autosomal or X linked variants were observed in 30 of them (50%). CONCLUSION: New genes recently identified in AMC represent 21% of causing genes in our cohort. A high proportion of de novo variants were observed indicating that this mechanism plays a prominent part in this developmental disease. Our data showed the added value of WES when compared with TES due to the larger clinical spectrum of some disease genes than initially described and the identification of novel genes.

Heterozygous loss of WBP11 function causes multiple congenital defects in humans and mice.

The genetic causes of multiple congenital anomalies are incompletely understood. Here, we report novel heterozygous predicted loss-of-function (LoF) and predicted damaging missense variants in the WW domain binding protein 11 (WBP11) gene in seven unrelated families with a variety of overlapping congenital malformations, including cardiac, vertebral, tracheo-esophageal, renal and limb defects. WBP11 encodes a component of the spliceosome with the ability to activate pre-messenger RNA splicing. We generated a Wbp11 null allele in mouse using CRISPR-Cas9 targeting. Wbp11 homozygous null embryos die prior to E8.5, indicating that Wbp11 is essential for development. Fewer Wbp11 heterozygous null mice are found than expected due to embryonic and postnatal death. Importantly, Wbp11 heterozygous null mice are small and exhibit defects in axial skeleton, kidneys and esophagus, similar to the affected individuals, supporting the role of WBP11 haploinsufficiency in the development of congenital malformations in humans. LoF WBP11 variants should be considered as a possible cause of VACTERL association as well as isolated Klippel-Feil syndrome, renal agenesis or esophageal atresia.

Activating Mutations of RRAS2 Are a Rare Cause of Noonan Syndrome.

Aberrant signaling through pathways controlling cell response to extracellular stimuli constitutes a central theme in disorders affecting development. Signaling through RAS and the MAPK cascade controls a variety of cell decisions in response to cytokines, hormones, and growth factors, and its upregulation causes Noonan syndrome (NS), a developmental disorder whose major features include a distinctive facies, a wide spectrum of cardiac defects, short stature, variable cognitive impairment, and predisposition to malignancies. NS is genetically heterogeneous, and mutations in more than ten genes have been reported to underlie this disorder. Despite the large number of genes implicated, about 10%-20% of affected individuals with a clinical diagnosis of NS do not have mutations in known RASopathy-associated genes, indicating that additional unidentified genes contribute to the disease, when mutated. By using a mixed strategy of functional candidacy and exome sequencing, we identify RRAS2 as a gene implicated in NS in six unrelated subjects/families. We show that the NS-causing RRAS2 variants affect highly conserved residues localized around the nucleotide binding pocket of the GTPase and are predicted to variably affect diverse aspects of RRAS2 biochemical behavior, including nucleotide binding, GTP hydrolysis, and interaction with effectors. Additionally, all pathogenic variants increase activation of the MAPK cascade and variably impact cell morphology and cytoskeletal rearrangement. Finally, we provide a characterization of the clinical phenotype associated with RRAS2 mutations.

GM3 synthase deficiency in non-Amish patients.

PURPOSE: Biallelic loss-of-function variants in ST3GAL5 cause GM3 synthase deficiency (GM3SD) responsible for Amish infantile epilepsy syndrome. All Amish patients carry the homozygous p.(Arg288Ter) variant arising from a founder effect. To date only 10 patients from 4 non-Amish families have been reported. Thus, the phenotypical spectrum of GM3SD due to other variants and other genetic backgrounds is still poorly known. METHODS: We collected clinical and molecular data from 16 non-Amish patients with pathogenic ST3GAL5 variants resulting in GM3SD. RESULTS: We identified 12 families originating from Reunion Island, Ivory Coast, Italy, and Algeria and carrying 6 ST3GAL5 variants, 5 of which were novel. Genealogical investigations and/or haplotype analyses showed that 3 of these variants were founder alleles. Glycosphingolipids quantification in patients' plasma confirmed the pathogenicity of 4 novel variants. All patients (N = 16), aged 2 to 12 years, had severe to profound intellectual disability, 14 of 16 had a hyperkinetic movement disorder, 11 of 16 had epilepsy and 9 of 16 had microcephaly. Other main features were progressive skin pigmentation anomalies, optic atrophy or pale papillae, and hearing loss. CONCLUSION: The phenotype of non-Amish patients with GM3SD is similar to the Amish infantile epilepsy syndrome, which suggests that GM3SD is associated with a narrow and severe clinical spectrum.

Extending the prenatal Noonan's phenotype by review of ultrasound and autopsy data.

OBJECTIVES: The antenatal phenotypic spectrum of Noonan Syndrome (NS) requires better characterization. METHODS: This multicenter retrospective observational included 16 fetuses with molecularly confirmed NS admitted for fetopathological examination between 2009 and 2016. RESULTS: Among 12 pathogenic variants (PV) in PTPN11 (80%), 5 (42%) fell between position c.179 and c.182. Ultrasound showed increased nuchal translucency (n = 13/16, 93%), increased nuchal fold after 15 weeks of gestation (n = 12/16, 75%), pleural effusions (n = 11/16, 69%), polyhydramnios (n = 9/16, 56%), hydrops (n = 7/16, 44%), cardiovascular (n = 6/16, 38%) and cerebral (n = 4/16, 25%) anomalies. Fetopathological examination found dysmorphic features in all cases, cardiovascular anomalies (n = 12/15, 80%), pulmonary hypoplasia (n = 10/15, 67%), effusions (n = 7/15, 47%) and neuropathological anomalies (n = 5/15, 33%). Hydrops was significantly (p = 0.02) more frequent in the four fetuses with RIT1, NRAS and RAF1 PV versus the 12 fetuses with PTPN11 PV. CONCLUSIONS: Increased nuchal translucency and nuchal fold is common in NS. Noonan Syndrome antenatal phenotype showed high in utero fetal death, hydrops, prenatal pleural effusion and pulmonary hypoplasia, although the inclusion of only deceased fetuses will have selected more severe phenotypes. Non-specific cardiovascular and neurological abnormalities should be added to NS antenatal phenotype. Next generation sequencing will help detect more genotypes, clarifying the prenatal phenotype and identifying genotype-phenotype correlations.

Genotype-first in a cohort of 95 fetuses with multiple congenital abnormalities: when exome sequencing reveals unexpected fetal phenotype-genotype correlations.

PURPOSE: Molecular diagnosis based on singleton exome sequencing (sES) is particularly challenging in fetuses with multiple congenital abnormalities (MCA). Indeed, some studies reveal a diagnostic yield of about 20%, far lower than in live birth individuals showing developmental abnormalities (30%), suggesting that standard analyses, based on the correlation between clinical hallmarks described in postnatal syndromic presentations and genotype, may underestimate the impact of the genetic variants identified in fetal analyses. METHODS: We performed sES in 95 fetuses with MCA. Blind to phenotype, we applied a genotype-first approach consisting of combined analyses based on variants annotation and bioinformatics predictions followed by reverse phenotyping. Initially applied to OMIM-morbid genes, analyses were then extended to all genes. We complemented our approach by using reverse phenotyping, variant segregation analysis, bibliographic search and data sharing in order to establish the clinical significance of the prioritised variants. RESULTS: sES rapidly identified causal variant in 24/95 fetuses (25%), variants of unknown significance in OMIM genes in 8/95 fetuses (8%) and six novel candidate genes in 6/95 fetuses (6%). CONCLUSIONS: This method, based on a genotype-first approach followed by reverse phenotyping, shed light on unexpected fetal phenotype-genotype correlations, emphasising the relevance of prenatal studies to reveal extreme clinical presentations associated with well-known Mendelian disorders.

Clinical spectrum of MTOR-related hypomelanosis of Ito with neurodevelopmental abnormalities.

PURPOSE: Hypomelanosis of Ito (HI) is a skin marker of somatic mosaicism. Mosaic MTOR pathogenic variants have been reported in HI with brain overgrowth. We sought to delineate further the pigmentary skin phenotype and clinical spectrum of neurodevelopmental manifestations of MTOR-related HI. METHODS: From two cohorts totaling 71 patients with pigmentary mosaicism, we identified 14 patients with Blaschko-linear and one with flag-like pigmentation abnormalities, psychomotor impairment or seizures, and a postzygotic MTOR variant in skin. Patient records, including brain magnetic resonance image (MRI) were reviewed. Immunostaining (n = 3) for melanocyte markers and ultrastructural studies (n = 2) were performed on skin biopsies. RESULTS: MTOR variants were present in skin, but absent from blood in half of cases. In a patient (p.[Glu2419Lys] variant), phosphorylation of p70S6K was constitutively increased. In hypopigmented skin of two patients, we found a decrease in stage 4 melanosomes in melanocytes and keratinocytes. Most patients (80%) had macrocephaly or (hemi)megalencephaly on MRI. CONCLUSION: MTOR-related HI is a recognizable neurocutaneous phenotype of patterned dyspigmentation, epilepsy, intellectual deficiency, and brain overgrowth, and a distinct subtype of hypomelanosis related to somatic mosaicism. Hypopigmentation may be due to a defect in melanogenesis, through mTORC1 activation, similar to hypochromic patches in tuberous sclerosis complex.

Phenotypic expansion of the BPTF-related neurodevelopmental disorder with dysmorphic facies and distal limb anomalies.

Neurodevelopmental disorder with dysmorphic facies and distal limb anomalies (NEDDFL), defined primarily by developmental delay/intellectual disability, speech delay, postnatal microcephaly, and dysmorphic features, is a syndrome resulting from heterozygous variants in the dosage-sensitive bromodomain PHD finger chromatin remodeler transcription factor BPTF gene. To date, only 11 individuals with NEDDFL due to de novo BPTF variants have been described. To expand the NEDDFL phenotypic spectrum, we describe the clinical features in 25 novel individuals with 20 distinct, clinically relevant variants in BPTF, including four individuals with inherited changes in BPTF. In addition to the previously described features, individuals in this cohort exhibited mild brain abnormalities, seizures, scoliosis, and a variety of ophthalmologic complications. These results further support the broad and multi-faceted complications due to haploinsufficiency of BPTF.

Immunopathological manifestations in Kabuki syndrome: a registry study of 177 individuals.

PURPOSE: Kabuki syndrome (KS) (OMIM 147920 and 300867) is a rare genetic disorder characterized by specific facial features, intellectual disability, and various malformations. Immunopathological manifestations seem prevalent and increase the morbimortality. To assess the frequency and severity of the manifestations, we measured the prevalence of immunopathological manifestations as well as genotype-phenotype correlations in KS individuals from a registry. METHODS: Data were for 177 KS individuals with KDM6A or KMT2D pathogenic variants. Questionnaires to clinicians were used to assess the presence of immunodeficiency and autoimmune diseases both on a clinical and biological basis. RESULTS: Overall, 44.1% (78/177) and 58.2% (46/79) of KS individuals exhibited infection susceptibility and hypogammaglobulinemia, respectively; 13.6% (24/177) had autoimmune disease (AID; 25.6% [11/43] in adults), 5.6% (10/177) with ≥2 AID manifestations. The most frequent AID manifestations were immune thrombocytopenic purpura (7.3% [13/177]) and autoimmune hemolytic anemia (4.0% [7/177]). Among nonhematological manifestations, vitiligo was frequent. Immune thrombocytopenic purpura was frequent with missense versus other types of variants (p = 0.027). CONCLUSION: The high prevalence of immunopathological manifestations in KS demonstrates the importance of systematic screening and efficient preventive management of these treatable and sometimes life-threatening conditions.