Association of a tagging single nucleotide polymorphism in the androgen receptor gene region with susceptibility to severe hypospadias in a Caucasian population.

Hypospadias is a congenital malformation and a milder form of 46,XY disorder of sexual development (DSD). In the present study, we investigated 13 haplotype tagging single nucleotide polymorphisms (SNPs) covering the steroid-5-alpha reductase (SRD5A2) and androgen receptor(AR) gene region, respectively, in a cohort consisting of 260 individuals with mild hypospadias and 77 with severe disease, in addition to 471 healthy male controls. The investigated genes are known to have an important role in the hormone-dependent stage of sexual development. Our study revealed one novel marker located in the AR gene region (rs5919436; g.67024320C>G) to be significantly associated with an increased risk of severe hypospadias (adjusted p value: 0.02; odds ratio: 2.98). In concordance with this finding, we detected an association of a haplotype tagged by the minor allele of rs5919436 (adjusted p value: 0.04). We further detected no association between the investigated disease and the haplotype tagging polymorphisms covering the SRD5A2 gene, which is of importance considering the conflicting results reported previously. In conclusion, our data implicate that the AR rs5919436 (g.67024320C>G) polymorphism may act as a novel genetic marker for increased susceptibility to severe hypospadias in Caucasians.

The p.G146A and p.P125P polymorphisms in the steroidogenic factor-1 (SF-1) gene do not affect the risk for hypospadias in Caucasians.

Hypospadias is a frequent congenital malformation in boys and is characterized by incomplete fusion of the urethral folds. The steroidogenic factor-1 (SF-1, NR5A1) gene plays a key role in hypothalamic-pituitary-steroidogenic organ development, and has previously been reported to be mutated in individuals with 46,XY disorder of sex development. Here, we investigated the role of SF-1 in hypospadias, a milder form of 46,XY disorder of sex development. We performed direct sequencing analysis of the SF-1 gene in 2 male Caucasian twins exhibiting very severe hypospadias, and in 95 Caucasian boys with mild and severe hypospadias. We further extended the analysis by investigating 332 mild and severe hypospadias cases and 422 male controls using TaqMan assays. Our sequencing revealed a novel heterozygous p.R313H (c.938G>A) missense mutation in each twin, and no mutations in the 95 Caucasian cases. Instead, a missense p.G146A (c.437G>C), and a silent known p.P125P (c.375C>T) polymorphism, respectively, was found in several of the latter cases. Further investigation of the 2 polymorphisms in the larger material of cases and controls showed no significant genotypic or allelic association. In conclusion, the SF-1 gene may not play a significant role in the development of hypospadias in Caucasians.

Hyperammonemia and neonatal cardiac failure.

Severe hyperammonemia (hyperNH3) in neonatal cardiac failure after cardiac surgery is rare. We report a case of a 2470-g female infant born at the week 37 of gestation with complex congenital heart disease (truncus arteriosus type III, interrupted aortic arch and tricuspid valve insufficiency) and hemodynamically non-significant intrahepatic arterio-venous malformation. She developed hyperNH3 (highest NH3 blood level: 467 µmol/L) without severe liver failure (INR of 1.9). The origin of the hyperNH3 was multifactorial including limited capacity of liver detoxification function due to congenital porto-caval shunt, liver ischemia, excessive protein intake and increased protein catabolic rate. HyperNH3 treatment partially succeeded in decreasing ammonia level and included discontinuation of protein intake, administration of phenylacetate and sodium benzoate. This case highlights the fact that NH3 detoxification by the liver has limitations for a neonate with multifactorial causes that decrease liver perfusion.

17-ß-hydroxysteroid dehydrogenase type 3 deficiency in three adult Iranian siblings.

17-ß-hydroxysteroid dehydrogenase type 3 (17-ß-HSD 3) deficiency is an autosomal recessive form of 46,XY disorder of sex development (DSD). To date, a total of 27 HSD17B3 gene mutations have been described in 46,XY patients exhibiting different phenotypes at birth and virilization at puberty, sometimes in association with gynecomastia. Herein, we investigate the 46,XY DSD in an Iranian family consisting of 7 siblings, 3 of which are affected and virilized at puberty. We clinically characterized these patients and performed direct DNA sequencing of the steroid 5-α-reductase type 2 (SRD5A2) and the HSD17B3 gene, respectively. We identified a homozygous mutation in the HSD17B3 gene (R80W; c.238C>G) in all affected siblings. No mutation was detected in the SRD5A2 gene. The detected mutation in the HSD17B3 gene was previously described in a newborn child, who died from other congenital malformations, and in a 12-year-old girl. Hence, our report adds novel value to the phenotype classification of 17-ß-HSD 3 deficiency.

Chromosome ideograms of the laboratory rat (Rattus norvegicus) based on high-resolution banding, and anchoring of the cytogenetic map to the DNA sequence by FISH in sample chromosomes.

A detailed banded ideogram representation of the rat chromosomes was constructed based on actual G-banded prometaphase chromosomes. The approach yielded 535 individual bands, a significant increase compared to previously presented ideograms. The new ideogram was adapted to the existing band nomenclature. The gene locus positions in the rat draft DNA sequence were compared to the chromosomal positions as determined by dual-color FISH, using rat (RNO) chromosomes 6 and 15 and a segment of RNO4 as sample regions. It was found that there was generally an excellent correlation in the chromosome regions tested between the relative gene position in the DNA molecules and the sub-chromosomal localization by FISH and subsequent information transfer on ideograms from measurements of chromosomal images. However, in the metacentric chromosome (RNO15), the correlation was much better in the short arm than in the long arm, suggesting that the centromeric region may distort the linear relationship between the chromosomal image and the corresponding DNA molecule.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces genetic changes in murine intestinal tumours and cells with ApcMin mutation.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the mutagenic heterocyclic amines derived from cooked meat. In previous animal studies, spontaneous tumour formation in B6(Min/+) mice was associated with somatic loss of the wild-type Apc+ allele by loss of the entire chromosome 18 or by recombination. The objective of this study was to examine genetic changes caused by PhIP-exposure in a mouse intestinal cell line and in tumours from hybrid mice by keeping track of the chromosomes carrying the two Apc alleles. We transformed the SV40 T-immortalised intestinal epithelial cell line IMCE, derived from the B6(Min/+) mice by exposure to N-OH-PhIP, and studied the effect on Apc status and chromosome 18. Eighteen transformed cultures were obtained and all of them had retained the Apc+ allele. Five of seven transformed cultures were tumorigenic after implantation in nude mice. Chromosomal analysis of these five cultures and the parent IMCE cell line showed that the IMCE cells were near-tetraploid with an average of 77 chromosomes/cell, while the tumorigenic cell cultures were all triploid to hyper-triploid with a range of 61-69 chromosomes/cell. The number of copies of chromosome 18 was about four in the IMCE line and this copy number was retained in the transformed lines derived from IMCE. Changes in chromosome 18 and Apc during tumour development in vivo were examined in spontaneously formed and PhIP-induced intestinal tumours from two hybrid mice strains, i.e. B6(Min/+) - a murine FAP model - crossed with either AKR/J or A/J. We evaluated the allelic status of Apc, and the heterogenic microsatellite markers D18Mit19 and D18Mit4, located at the upper and lower ends of chromosome 18, respectively. In tumours from untreated animals, instability in the D18Mit19 and Apc was observed. Upon PhIP exposure, the B6(Min/A+) hybrid mouse tumours differed distinctly in genetic profile from those obtained from untreated animals and we detected three genetically different tumour groups, all of which had apparently retained Apc+. One group had allelic balance between the Apc(Min) and Apc+, the second had allelic imbalance between the Apc and D18Mit4 alleles, indicative of chromosomal stability in the first group and instability in the lower end of chromosome 18 in the second group, respectively. The third group showed variable allelic status of the three markers. A similar change in genetic profile was also seen in intestinal tumours of PhIP-exposed B6(Min/AKR+) hybrid mice, but it was less pronounced. Chromosomal breaks and/or recombinational events could be alternative explanations for the observed allelic imbalances in chromosome 18 markers in intestinal tumours from PhIP-exposed mice.