G6PD genetic variations in neonatal Hyperbilirubinemia in Indonesian Deutromalay population

Background: Neonatal jaundice is a common finding in newborns in Asia, including Indonesia. In some cases, the serum total bilirubin levels exceeds the 95th percentile for hours of life (neonatal hyperbilirubinemia). Severe neonatal hyperbilirubinemia (NH) could lead to kernicterus and neonatal death. Glucose-6-Phosphage Dehydrogenase (G6PD) genetic variations and deficiency have been reported in several studies to be associated with NH. This study aimed to analyze the G6PD genetic variations a

Whole exome sequencing coupled with unbiased functional analysis reveals new Hirschsprung disease genes

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Fine mapping of the 9q31 Hirschsprung’s disease locus

Hirschsprung’s disease (HSCR) is a congenital disorder characterised by the absence of ganglia along variable lengths of the intestine. The RET gene is the major HSCR gene. Reduced penetrance of RET mutations and phenotypic variability suggest the involvement of additional modifying genes in the disease. A RET-dependent modifier locus was mapped to 9q31 in families bearing no coding sequence (CDS) RET mutations. Yet, the 9q31 causative locus is to be identified. To fine-map the 9q31 region, we genotyped 301 tag-SNPs spanning 7 Mb on 137 HSCR Dutch trios. This revealed two HSCR-associated regions that were further investigated in 173 Chinese HSCR patients and 436 controls using the genotype data obtained from a genome-wide association study recently conducted. Within one of the two identified regions SVEP1 SNPs were found associated with Dutch HSCR patients in the absence of RET mutations. This ratifies the reported linkage to the 9q31 region in HSCR families with no RET CDS mutations. However, this finding could not be replicated. In Chinese, HSCR was found associated with IKBKAP. In contrast, this association was stronger in patients carrying RET CDS mutations with p = 5.10 × 10−6 [OR = 3.32 (1.99, 5.59)] after replication. The HSCR-association found for IKBKAP in Chinese suggests population specificity and implies that RET mutation carriers may have an additional risk. Our finding is supported by the role of IKBKAP in the development of the nervous system

Whole exome sequencing coupled with unbiased functional analysis reveals new Hirschsprung disease genes

Background: Hirschsprung disease (HSCR), which is congenital obstruction of the bowel, results from a failure of enteric nervous system (ENS) progenitors to migrate, proliferate, differentiate, or survive within the distal intestine. Previous studies that have searched for genes underlying HSCR have focused on ENS-related pathways and genes not fitting the current knowledge have thus often been ignored. We identify and validate novel HSCR genes using whole exome sequencing (WES), burden tests, in silico prediction, unbiased in vivo analyses of the mutated genes in zebrafish, and expression analyses in zebrafish, mouse, and human. Results: We performed de novo mutation (DNM) screening on 24 HSCR trios. We identify 28 DNMs in 21 different genes. Eight of the DNMs we identified occur in RET, the main HSCR gene, and the remaining 20 DNMs reside in genes not reported in the ENS. Knockdown of all 12 genes with missense or loss-of-function DNMs showed that the orthologs of four genes (DENND3, NCLN, NUP98, and TBATA) are indispensable for ENS development in zebrafish, and these results were confirmed by CRISPR knockout. These genes are also expressed in human and mouse gut and/or ENS progenitors. Importantly, the encoded proteins are linked to neuronal processes shared by the central nervous system and the ENS. Conclusions: Our data open new fields of investigation into HSCR pathology and provide novel insights into the development of the ENS. Moreover, the study demonstrates that functional analyses of genes carrying DNMs are warranted to delineate the full genetic architecture of rare complex diseases

Literature review: enteric nervous system development, genetic and epigenetic regulation in the etiology of Hirschsprung's disease

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system (ENS) derived from neural crest cells (NCCs), which affects their migration, proliferation, differentiation, or preservation in the digestive tract, resulting in aganglionosis in the distal intestine. The regulation of both NCCs and the surrounding environment involves various genes, signaling pathways, transcription factors, and morphogens. Therefore, changes in gene expression during the development of the ENS may contribute to the pathogenesis of HSCR.This review discusses several mechanisms involved in the development of ENS, confirming that deviant genetic and epigenetic patterns, such as DNA methylation, histone modification, and microRNA (miRNA) regulation, can contribute to the development of neurocristopathy. Specifically, the epigenetic regulation of miRNA expression and its relationship to cellular interactions and gene activation through various major pathways in Hirschsprung's disease will be discussed

Fine mapping of Hirschsprung’s disease loci in 9q31

721/W/Poster Board #379Hirschsprung’s disease (HSCR) is a congenital disorder in which there is an absence of ganglion cells in variable portions of the lower digestive tract, according to which patients are classified. The RET gene is the largest risk factor in HSCR, although reduced penetrance of RET mutations, absence of RET mutations in some patients, and variable expression of the HSCR phenotype indicate that more than one gene is involved. A RET-dependent modifier which segregates in families harboring no or hypomorphic RET mutations was mapped to 9q31. Fine mapping of the region performed on 142 Dutch trios by genotyping 370 tag-SNPs spanning approximately 7 Mb (from 108.5-115.5 Mb) of 9q31 on an Illumina GoldenGate platform identified two different 9q31 HSCR-associated regions in which genes with biological plausibility lie. Since evaluation of an association in a population of different origin from that of the initial finding increases the association confidence and, since linkage disequilibrium (LD) differences across populations can be used to narrow the regions of interest, we genotyped 181 Chinese HSCR patients and 179 controls for 38 tag-SNPs chosen from the CHB population spanning the 9q31 regions of interest. In addition, we made use of genotype data for the 9q31 region obtained from a genome-wide association study recently conducted in Chinese HSCR patients. Only one of the two 9q31 HSCR-associated regions identified in the Dutch population was associated in Chinese (p = 0.021), although the most associated SNPs within the region differed, probably due to differences in LD and/or different genotyping densities. Importantly, the associated region encompasses IKBKAP and CTNNAL1, which have been linked to neurodevelopmental disorders.The 59th Annual Meeting of the American Society of Human Genetics (ASHG), Honolulu, HI., 20-24 October 2009