Lysosphingolipid urine screening test using mass spectrometry for the early detection of lysosomal storage disorders.

Background: Sphingolipidoses are caused by a defective sphingolipid catabolism, leading to an accumulation of several glycolipid species in tissues and resulting in neurotoxicity and severe systemic manifestations. Methods & results: Urine samples from controls and patients were purified by solid-phase extraction prior to the analysis by ultra-high-performance liquid chromatography (UPLC) combined with MS/MS. A UPLC-MS/MS method for the analysis of 21 urinary creatinine-normalized biomarkers for eight diseases was developed and validated. Conclusion: Considering the growing demand to identify patients with different sphingolipidoses early and reliably, this methodology will be applied for high-risk screening to target efficiently patients with various sphingolipidoses.

DOORS syndrome and a recurrent truncating ATP6V1B2 variant.

PURPOSE: Biallelic variants in TBC1D24, which encodes a protein that regulates vesicular transport, are frequently identified in patients with DOORS (deafness, onychodystrophy, osteodystrophy, intellectual disability [previously referred to as mental retardation], and seizures) syndrome. The aim of the study was to identify a genetic cause in families with DOORS syndrome and without a TBC1D24 variant. METHODS: Exome or Sanger sequencing was performed in individuals with a clinical diagnosis of DOORS syndrome without TBC1D24 variants. RESULTS: We identified the same truncating variant in ATP6V1B2 (NM_001693.4:c.1516C>T; p.Arg506*) in nine individuals from eight unrelated families with DOORS syndrome. This variant was already reported in individuals with dominant deafness onychodystrophy (DDOD) syndrome. Deafness was present in all individuals, along with onychodystrophy and abnormal fingers and/or toes. All families but one had developmental delay or intellectual disability and five individuals had epilepsy. We also describe two additional families with DDOD syndrome in whom the same variant was found. CONCLUSION: We expand the phenotype associated with ATP6V1B2 and propose another causal gene for DOORS syndrome. This finding suggests that DDOD and DOORS syndromes might lie on a spectrum of clinically and molecularly related conditions.

UBR7 functions with UBR5 in the Notch signaling pathway and is involved in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism.

The ubiquitin-proteasome system facilitates the degradation of unstable or damaged proteins. UBR1-7, which are members of hundreds of E3 ubiquitin ligases, recognize and regulate the half-life of specific proteins on the basis of their N-terminal sequences ("N-end rule"). In seven individuals with intellectual disability, epilepsy, ptosis, hypothyroidism, and genital anomalies, we uncovered bi-allelic variants in UBR7. Their phenotype differs significantly from that of Johanson-Blizzard syndrome (JBS), which is caused by bi-allelic variants in UBR1, notably by the presence of epilepsy and the absence of exocrine pancreatic insufficiency and hypoplasia of nasal alae. While the mechanistic etiology of JBS remains uncertain, mutation of both Ubr1 and Ubr2 in the mouse or of the C. elegans UBR5 ortholog results in Notch signaling defects. Consistent with a potential role in Notch signaling, C. elegans ubr-7 expression partially overlaps with that of ubr-5, including in neurons, as well as the distal tip cell that plays a crucial role in signaling to germline stem cells via the Notch signaling pathway. Analysis of ubr-5 and ubr-7 single mutants and double mutants revealed genetic interactions with the Notch receptor gene glp-1 that influenced development and embryo formation. Collectively, our findings further implicate the UBR protein family and the Notch signaling pathway in a neurodevelopmental syndrome with epilepsy, ptosis, and hypothyroidism that differs from JBS. Further studies exploring a potential role in histone regulation are warranted given clinical overlap with KAT6B disorders and the interaction of UBR7 and UBR5 with histones.

A variant of neonatal progeroid syndrome, or Wiedemann-Rautenstrauch syndrome, is associated with a nonsense variant in POLR3GL.

Neonatal progeroid syndrome, also known as Wiedemann-Rautenstrauch syndrome, is a rare condition characterized by severe growth retardation, apparent macrocephaly with prominent scalp veins, and lipodystrophy. It is caused by biallelic variants in POLR3A, a gene encoding for a subunit of RNA polymerase III. All variants reported in the literature lead to at least a partial loss-of-function (when considering both alleles together). Here, we describe an individual with several clinical features of neonatal progeroid syndrome in whom exome sequencing revealed a homozygous nonsense variant in POLR3GL (NM_032305.2:c.358C>T; p.(Arg120Ter)). POLR3GL also encodes a subunit of RNA polymerase III and has recently been associated with endosteal hyperostosis and oligodontia in three patients with a phenotype distinct from the patient described here. Given the important role of POLR3GL in the same complex as the protein implicated in neonatal progeroid syndrome, the nature of the variant identified, our RNA studies suggesting nonsense-mediated decay, and the clinical overlap, we propose POLR3GL as a gene causing a variant of neonatal progeroid syndrome and therefore expand the phenotype associated with POLR3GL variants.

Retrospective analysis of fetal vertebral defects: Associated anomalies, etiologies, and outcome.

Our objectives were to describe fetal cases of vertebral defects (VD), assess the diagnostic yield of fetal chromosomal analysis for VD and determine which investigations should be performed when evaluating fetal VD. We performed a retrospective chart review for fetuses with VD seen between 2006 and 2015. Cases were identified from CHU Sainte-Justine's prenatal clinic visits, postmortem fetal skeletal surveys, and medical records. Cases with neural tube defects were excluded. Sixty-six fetuses with VD were identified at a mean gestational age of 20 weeks. Forty-seven (71.2%) had associated antenatal anomalies, most commonly genitourinary, skeletal/limb, and cardiac anomalies. Thirteen mothers (19.7%) had pregestational diabetes (95% CI [10.1%-29.3%]). Fifty-three cases had chromosomal analysis. Three had abnormal results (5.6%): trisomy 13, trisomy 22, and 9q33.1q34.11 deletion. Thirty-four (51.5%) pregnancies were terminated, one led to intrauterine fetal demise and 31 (46.9%) continued to term. Of 27 children who survived the neonatal period, 21 had congenital scoliosis and 3 had spondylocostal dysostosis. Seven had developmental delay. In conclusion, prenatal evaluation of fetuses with VD should include detailed morphological assessment (including fetal echocardiogram), maternal diabetes screening, and chromosomal microarray if non-isolated. Our findings provide guidance about management and counseling after a diagnosis of fetal VD.

Missense Variants in the Histone Acetyltransferase Complex Component Gene TRRAP Cause Autism and Syndromic Intellectual Disability.

Acetylation of the lysine residues in histones and other DNA-binding proteins plays a major role in regulation of eukaryotic gene expression. This process is controlled by histone acetyltransferases (HATs/KATs) found in multiprotein complexes that are recruited to chromatin by the scaffolding subunit transformation/transcription domain-associated protein (TRRAP). TRRAP is evolutionarily conserved and is among the top five genes intolerant to missense variation. Through an international collaboration, 17 distinct de novo or apparently de novo variants were identified in TRRAP in 24 individuals. A strong genotype-phenotype correlation was observed with two distinct clinical spectra. The first is a complex, multi-systemic syndrome associated with various malformations of the brain, heart, kidneys, and genitourinary system and characterized by a wide range of intellectual functioning; a number of affected individuals have intellectual disability (ID) and markedly impaired basic life functions. Individuals with this phenotype had missense variants clustering around the c.3127G>A p.(Ala1043Thr) variant identified in five individuals. The second spectrum manifested with autism spectrum disorder (ASD) and/or ID and epilepsy. Facial dysmorphism was seen in both groups and included upslanted palpebral fissures, epicanthus, telecanthus, a wide nasal bridge and ridge, a broad and smooth philtrum, and a thin upper lip. RNA sequencing analysis of skin fibroblasts derived from affected individuals skin fibroblasts showed significant changes in the expression of several genes implicated in neuronal function and ion transport. Thus, we describe here the clinical spectrum associated with TRRAP pathogenic missense variants, and we suggest a genotype-phenotype correlation useful for clinical evaluation of the pathogenicity of the variants.

Genetic Testing in a Cohort of Complex Esophageal Atresia.

The objective of the present study is to describe a cohort of complex esophageal atresia and the yield of genetic tests performed for such patients. We selected 45 patients with complex esophageal atresia (EA), namely those having at least one associated anomaly. We reviewed their medical records to assess clinical features, other diagnoses, and genetic investigations. Most of the patients had a diagnosis of VACTERL association (56%) with no genetic variant identified. Interestingly, 5 patients in the cohort (11%) had a right pulmonary hypoplasia or agenesis. A majority of our cohort (73%) had genetic testing; 60% were karyotyped (abnormal in 4 of the 27 patients tested), 31% had aCGH (abnormal in 1 of the 14 patients tested), and 31% had diepoxybutane (DEB) testing for Fanconi anemia (abnormal in 2 of the 14 patients tested). One patient had exome sequencing studies, but no candidate gene was identified. Various anomalies were associated with EA, and overall a genetic variant could be identified in 7 of the 33 patients tested. Chromosomal studies such as aCGH and chromosomal breakage studies should be considered, and their yield varied between 7 and 14%. Other genetic investigations such as exome sequencing could possibly have even higher yields but will need to be assessed in a large cohort. Improved genetic diagnoses in EA may improve the management of these patients by directing specific surveillance and management schemes.

Retrospective Analysis of Congenital Scoliosis: Associated Anomalies and Genetic Diagnoses.

STUDY DESIGN: Retrospective study of a series of 286 patients with congenital scoliosis (CS). OBJECTIVE: To describe a large cohort of patients with CS and to propose an algorithm for genetic investigations SUMMARY OF BACKGROUND DATA.: CS is characterized by a spine curvature due to congenital malformations of the vertebrae and is frequently associated to other anomalies. The underlying causes remain unclear in most patients, although we know that genetics plays a role in the development of vertebral defects. METHODS: Institutional review board approval was obtained. We performed a retrospective study by consulting the hospital charts of 286 patients with CS seen at the CHU Sainte-Justine, Montreal, from 2004 to 2015. We compile information on radiological findings, associated malformations, and genetic tests. RESULTS: Results showed that 67.1% of patients had associated anomalies affecting different systems. Only a minority of patients had a syndromic diagnosis to explain their CS. Nevertheless, array comparative genomic hybridization performed in a minority of patients showed a high detection rate (31.3% had a chromosomal anomaly among 32 tested). CONCLUSION: We suggest that every patient with CS should have thorough investigations to rule out associated anomalies and that different genetic tests should be offered according to the associated clinical findings. LEVEL OF EVIDENCE: 4.