Lisa Anderson

Fryns Syndrome Associated with Recessive Mutations in PIGN in two Separate Families

Fryns syndrome is an autosomal recessive condition characterized by congenital diaphragmatic hernia (CDH), dysmorphic facial features, distal digital hypoplasia, and other associated malformations, and is the most common syndromic form of CDH. No gene has been associated with this condition. Whole‐exome sequence data from two siblings and three unrelated individuals with Fryns syndrome were filtered for rare, good quality, coding mutations fitting a recessive inheritance model. Compound heterozygous mutations in PIGN were identified in the siblings, with appropriate parental segregation: a novel STOP mutation (c.1966C>T: p.Glu656X) and a rare (minor allele frequency <0.001) donor splice site mutation (c.1674+1G>C) causing skipping of exon 18 and utilization of a cryptic acceptor site in exon 19. A further novel homozygous STOP mutation in PIGN (c.694A>T: p.Lys232X) was detected in one unrelated case. All three variants affected highly conserved bases. The two remaining cases were negative for PIGN mutations. Mutations in PIGN have been reported in cases with multiple congenital anomalies, including one case with syndromic CDH. Fryns syndrome can be caused by recessive mutations in PIGN. Whether PIGN affects other syndromic and non‐syndromic forms of CDH warrants investigation.

Epigenetic and gene expression analysis of ankylosing spondylitis-associated loci implicate immune cells and the gut in the disease pathogenesis

Ankylosing spondylitis (AS) is a common immune-mediated arthropathy primarily affecting the spine and pelvis. Most AS patients have subclinical intestinal inflammation, suggesting the gut microbiome and the immune response play a role in pathogenesis. Susceptibility to AS is primarily genetic, and at least 114 susceptibility variants have been identified to date. We applied bioinformatic methods utilizing epigenetic and gene and protein expression data to identify the cell types through which AS-associated variants operate. Variants were enriched in transcriptionally regulated regions in monocytes, CD4+ and CD8+ T cells, natural killer cells, regulatory T cells and B cells and mucosa from the small intestine, sigmoid colon and rectum. Weak signals were detected in bone cells, consistent with bone disease being a secondary manifestation. RNA sequencing of blood cells from AS patients and controls identified differentially expressed genes. Interrogation of expression databases showed that the upregulated genes were enriched in monocytes and downregulated genes were enriched in CD8+ T cells and natural killer cells. Gene Ontology term enrichment analysis identified microbes and the gut in the aetiology of AS. These findings identify the key immune cell types that drive the disease, and further highlight the involvement of the gut microbiome in the pathogenesis of AS.

Whole-exome sequencing in amyotrophic lateral sclerosis suggests NEK1 is a risk gene in Chinese

BackgroundAmyotrophic lateral sclerosis (ALS) is a progressive neurological disease characterised by the degeneration of motor neurons, which are responsible for voluntary movement. There remains limited understanding of disease aetiology, with median survival of ALS of three years and no effective treatment. Identifying genes that contribute to ALS susceptibility is an important step towards understanding aetiology. The vast majority of published human genetic studies, including for ALS, have used samples of European ancestry. The importance of trans-ethnic studies in human genetic studies is widely recognised, yet a dearth of studies of non-European ancestries remains. Here, we report analyses of novel whole-exome sequencing (WES) data from Chinese ALS and control individuals.MethodsWES data were generated for 610 ALS cases and 460 controls drawn from Chinese populations. We assessed evidence for an excess of rare damaging mutations at the gene level and the gene set level, considering only singleton variants filtered to have allele frequency less than 5 × 10–5 in reference databases. To meta-analyse our results with a published study of European ancestry, we used a Cochran–Mantel–Haenszel test to compare gene-level variant counts in cases vs controls.ResultsNo gene passed the genome-wide significance threshold with ALS in Chinese samples alone. Combining rare variant counts in Chinese with those from the largest WES study of European ancestry resulted in three genes surpassing genome-wide significance: TBK1 (p = 8.3 × 10–12), SOD1 (p = 8.9 × 10–9) and NEK1 (p = 1.1 × 10–9). In the Chinese data alone, SOD1 and NEK1 were nominally significantly associated with ALS (p = 0.04 and p = 7 × 10–3, respectively) and the case/control frequencies of rare coding variants in these genes were similar in Chinese and Europeans (SOD1: 1.5%/0.2% vs 0.9%/0.1%, NEK1 1.8%/0.4% vs 1.9%/0.8%). This was also true for TBK1 (1.2%/0.2% vs 1.4%/0.4%), but the association with ALS in Chinese was not significant (p = 0.14).ConclusionsWhile SOD1 is already recognised as an ALS-associated gene in Chinese, we provide novel evidence for association of NEK1 with ALS in Chinese, reporting variants in these genes not previously found in Europeans.

Whole-exome sequencing for mutation detection in pediatric disorders of insulin secretion: Maturity onset diabetes of the young and congenital hyperinsulinism

To assess the utility of whole‐exome sequencing (WES) for mutation detection in maturity‐onset diabetes of the young (MODY) and congenital hyperinsulinism (CHI). MODY and CHI are the two commonest monogenic disorders of glucose‐regulated insulin secretion in childhood, with 13 causative genes known for MODY and 10 causative genes identified for CHI. The large number of potential genes makes comprehensive screening using traditional methods expensive and time‐consuming.

Comprehensive genetic screening: the prevalence of MODY gene variants in a population-based childhood diabetes cohort

Maturity‐onset diabetes of the young (MODY) is caused by autosomal dominant mutations in one of 13 confirmed genes. Estimates of MODY prevalence vary widely, as genetic screening is usually restricted based on clinical features, even in population studies. We aimed to determine prevalence of MODY variants in a large and unselected pediatric diabetes cohort.

Point mutation in p14ARF-specific exon 1β of CDKN2A causing familial melanoma and astrocytoma

Research letter Dear Editor, Rarely, melanoma is dominantly inherited, with CDKN2A mutations accounting for > 85% of mutation‐positive families.1 CDKN2A encodes two, nonhomologous proteins, p16 and p14ARF, with individually unique first exons (1α and 1β, respectively) and alternative reading frames. Over 95% of the CDKN2A mutations in familial melanoma occur in the p16 transcript...