Identification of novel mutations in the ABCA12 gene,c.1857delA and c.5653–5655delTAT,causing harlequin ichthyosis

Harlequin ichthyosis (HI) is a severe autosomal recessive developmental disorder of the skin that is frequently but not always fatal in the first few days of life. In HI, mutations in both ABCA12 gene alleles must have a severe impact on protein function and most mutations are truncating. The presence of at least one nontruncating mutation (predicting a residual protein function) usually causes a less severe congenital ichthyosis (lamellar ichthyosis or congenital ichthyosiform erythroderma). Here we report on a girl with severe HI diagnosed by prenatal ultrasound at 33 5/7 week gestation. Ultrasound findings included ectropion, eclabium, deformed nose, hands and feet, joint contractures, hyperechogenic amniotic fluid and polyhydramnion. After birth, palliative treatment was provided and she died on her first day of life. Sequence analysis of the ABCA12 gene identified two novel mutations, c.1857delA (predicting p.Lys619*) in exon 15 and c.5653–5655delTAT (predicting p.1885delTyr) in exon 37, each in heterozygous state. The c.5653–5655delTAT mutation is not truncating, but the deleted tyrosine at position 1885 is perfectly conserved among vertebrates and molecular studies evaluated the mutation as probably disease causing and damaging.     

Prenatal diagnosis and molecular cytogenetic characterization of a de novo proximal interstitial deletion of chromosome 4p (4p15.2→p14)

We present prenatal diagnosis of de novo proximal interstitial deletion of chromosome 4p (4p15.2→p14) and molecular cytogenetic characterization of the deletion using uncultured amniocytes. We review the phenotypic abnormalities of previously reported patients with similar proximal interstitial 4p deletions, and we discuss the functions of the genes of RBPJ, CCKAR, STIM2, PCDH7 and ARAP2 that are deleted within this region.     

Prenatal diagnosis of pure partial monosomy 18p associated with holoprosencephaly and congenital heart defects

We applied CMA to detect chromosomal variations during a prenatal diagnosis and detected a 4.5 Mb pure microdeletion at 18p11.3 that was not detected by conventional karyotyping. Fluorescent in situ hybridization (FISH) analysis was performed to confirm the deletion. Accurate breakpoints of the deletion in this patient were used to build correlations between monosomy 18p and the concomitant phenotypes, particularly holoprosencephaly (HPE), which is rarely reported in monosomy 18p11.3.     

Prenatal diagnosis and molecular cytogenetic characterization of de novo pure partial trisomy 6p associated with microcephaly,craniosynostosis and abnormal maternal serum biochemistry

We present prenatal diagnosis and molecular cytogenetic characterization of de novo pure trisomy 6p22.3 → p25.3 encompassing BMP6 in a fetus associated with microcephaly and craniosynostosis on prenatal ultrasound, abnormal maternal serum biochemistry of a low PAPP-A level in the first-trimester combined test, and a karyotype of 46,XX,der(22)t(6;22)(p22.3;p13)dn. The present case demonstrates the usefulness of rapid prenatal identification of the origin of the extra chromosome material on the short arm of an acrocentric chromosome by spectral karyotyping, fluorescence in situ hybridization and array comparative genomic hybridization. We review the phenotypic abnormality of craniosynostosis in previously reported patients with partial trisomy 6p. We discuss the genotype–phenotype correlation of the involved gene of BMP6 in this case.     

Chromosome 18p deletion syndrome presenting holoprosencephaly and premaxillary agenesis: Prenatal diagnosis and aCGH characterization using uncultured amniocytes

We present prenatal diagnosis of a de novo distal 18p deletion involving 14.06 Mb at 18p11.32–p11.21 by aCGH using uncultured amniocytes in a pregnancy with fetal holoprosencephaly and premaxillary agenesis. QF-PCR analysis showed that distal 18p deletion was from maternal origin. Metaphase FISH analysis confirmed haploinsufficiency of TGIF. We discuss the functions of the genes that are deleted within this region. The present case shows the usefulness of applying aCGH on uncultured amniocytes for rapid aneuploidy diagnosis in cases with prenatally detected fetal structural abnormalities.     

Chromosome 17p13.3 deletion syndrome: aCGH characterization,prenatal findings and diagnosis,and literature review

We report a molecular cytogenetic characterization of 17p13.3 deletion syndrome by array comparative genomic hybridization (aCGH), fluorescence in situ hybridization (FISH) and quantitative polymerase chain reaction (qPCR) in a fetus with lissencephaly, corpus callosum dysgenesis, ventriculomegaly, microcephaly, intrauterine growth restriction (IUGR), polyhydramnios and single umbilical artery. aCGH analysis revealed a 3.17-Mb deletion at 17p13.3, or arr [hg19] 17p13.3 (0–3,165,530)×1. The qPCR assays revealed a maternal origin of the deletion. Metaphase FISH analysis detected the absence of the LIS1 probe signal on the aberrant chromosome 17. The karyotype was 46,XX,del(17)(p13.3). We review the literature of chromosome 17p13.3 deletion syndrome with prenatal findings and diagnosis, and suggest that prenatal ultrasound detection of central nervous system anomalies such as lissencephaly, corpus callosum dysgenesis/agenesis, ventriculomegaly and microcephaly associated with IUGR, polyhydramnios, congenital heart defects, abdominal wall defects and renal abnormalities should include a differential diagnosis of chromosome 17p13.3 deletion syndrome.     

H-Ras activation promotes cytoplasmic accumulation and phosphoinositide 3-OH kinase association of beta-catenin in epidermal keratinocytes.

The mechanisms underlying downregulation of the cadherin/catenin complexes and beta-catenin signaling during tumor progression are not fully understood. We have analyzed the effect of oncogenic H-Ras on E-cadherin/catenin complex formation/stabilization and beta-catenin distribution in epidermal keratinocytes. Microinjection or stable expression of V12Ras into keratinocytes promotes the loss of E-cadherin and alpha-catenin and relocalization of beta-catenin to the cytoplasm and nucleus. Moreover, these effects are dependent on PI3K (phosphoinositide 3-OH kinase) activity. Interestingly, a strong association of p85alpha and p110alpha subunits of PI3K with beta-catenin is induced in V12Ras-expressing keratinocytes, and in vitro binding assays show a direct interaction between beta-catenin and p85alpha. Overexpression of either V12Ras or constitutively active p110alpha induces metabolic stabilization of beta-catenin and promotes its accumulation in cytoplasmic and nuclear pools. In addition, the interaction of beta-catenin with the adenomatous polyposis coli protein is blocked in V12Ras and p110alpha transformants though no changes in glycogen synthase kinase 3 beta activity could be detected. Nevertheless, in V12Ras transformants the in vivo phosphorylation of beta-catenin in Ser residues is strongly decreased. These results indicate that H-Ras activation induces the relocalization and cytoplasmic stabilization of beta-catenin by a mechanism involving its interaction with PI3K.     

Two novel isovaleryl-CoA dehydrogenase gene mutations in a Chinese infant

Isovaleric acidemia (IVA) is a rare inherited metabolic disease caused by a deficiency in isovaleryl-CoA dehydrogenase (IVD). Newborn screening with tandem mass spectrometry leads to early identification of individuals with risk of IVA. The family specific mutations are useful for prenatal diagnosis. Molecular genetic analysis helps to further confirm the clinical diagnosis of IVA. We describe here the clinical and metabolic features of a Chinese infant with early onset IVA. Sequence analysis of the IVD gene identifies compound heterozygous mutations in this patient, c.39G > A (p.W13X) nonsense mutation and c.597C > G (p.I199M) missense mutation, both of which are previously unreported. Structural analyses suggest that the p.I199M missense mutation may destabilize the IVD monomer structure and affect the interaction between IVD and flavin adenine dinucleotide. Both the clinical and genetic features of this patient help to further expand our knowledge of IVA.     

Tryptophan (W) at position 37 of murine IL-12/IL-23 p40 is mandatory for binding to IL-12Rβ1 and subsequent signal transduction

Interleukin (IL)-12 and IL-23 are composite cytokines consisting of p35/p40 and p19/p40, respectively, which signal via the common IL-12 receptor β1 (IL-12Rβ1) and the cytokine-specific receptors IL-12Rβ2 and IL-23R. Previous data showed that the p40 component interacts with IL-12Rβ1, whereas p19 and p35 subunits solely bind to IL-23R and IL-12Rβ2, resulting in tetrameric signaling complexes. In the absence of p19 and p35, p40 forms homodimers and may induce signaling via IL-12Rβ1 homodimers. The critical amino acids of p19 and p35 required for binding to IL-23R and IL-12Rβ2 are known, and two regions of p40 critical for binding to IL-12Rβ1 have recently been identified. In order to characterize the involvement of the N-terminal region of p40 in binding to IL-12Rβ1, we generated deletion variants of the p40-p19 fusion cytokine. We found that an N-terminal deletion variant missing amino acids M23 to P39 failed to induce IL-23-dependent signaling and did not bind to IL-12Rβ1, whereas binding to IL-23R was maintained. Amino acid replacements showed that p40W37K largely abolished IL-23-induced signal transduction and binding to IL-12Rβ1, but not binding to IL-23R. Combining p40W37K with D36K and T38K mutations eliminated the biological activity of IL-23. Finally, homodimeric p40D36K/W37K/T38K did not interact with IL-12Rβ1, indicating binding of homodimeric p40 to IL-12Rβ1 is comparable to the interaction of IL-23/IL-12 and IL-12Rβ1. In summary, we have defined D36, W37, and T38 as hotspot amino acids for the interaction of IL-12/IL-23 p40 with IL-12Rβ1. Structural insights into cytokine–cytokine receptor binding are important to develop novel therapeutic strategies.     

2D:4D ratios in the first 2 years of life: Stability and relation to testosterone exposure and sensitivity

The relative lengths of the 2nd and 4th digits (2D:4D) may provide an easily measurable and stable anthropometric index of prenatal androgen exposure, but no study has examined the development of 2D:4D in infancy and the potential impact of neonatal testosterone levels. We collected 2D:4D ratios from 364 children between 0 and 2 years of age. Saliva samples were collected from 236 of these children 3 months after birth and analyzed for testosterone. In addition, 259 children provided DNA samples which were genotyped for the CAG repeat polymorphism in the androgen receptor. There was substantial variability across age in 2D:4D. Sex differences were small compared to adults and did not consistently reach statistical significance. This suggests that 2D:4D may not function well as a proxy measure of prenatal testosterone exposure in infancy. In addition, the interaction of salivary T and CAG repeats predicted right hand digit ratio at 12 months and left hand digit ratio at 12 months and 24 months in males. The interaction of salivary testosterone and CAG repeat length also predicted change in left hand 2D:4D from 2 weeks to 12 months in males. This suggests that 2D:4D in adults may reflect, in part, neonatal testosterone exposure. No significant relationships were observed within females. No significant relationships were observed when salivary testosterone and CAG repeats were examined independent of each other. Results have important implications for the design and interpretation of studies which use 2D:4D as a proxy measure of prenatal testosterone exposure.     

KRT9 gene mutation as a reliable indicator in the prenatal molecular diagnosis of epidermolytic palmoplantar keratoderma

Epidermolytic palmoplantar keratoderma (EPPK) is the most frequent form of such keratodermas. It is inherited in an autosomal dominant pattern and is clinically characterized by diffuse yellowish thickening of the skin on the palms and soles with erythematous borders during the first weeks or months after birth. EPPK is generally caused by mutations of the KRT9 gene. More than 26 KRT9 gene mutations responsible for EPPK have been described (Human Intermediate Filament Database, www.interfil.org), and many of these variants are located within the highly-conserved coil 1A region of the α-helical rod domain of keratin 9. Unfortunately, there is no satisfactory treatment for EPPK. Thus, prenatal molecular diagnosis or pre-pregnancy diagnosis is crucial and benefits those affected who seek healthy descendants. In the present study, we performed amniotic fluid-DNA-based prenatal testing for three at-risk pregnant EPPK women from three unrelated southern Chinese families who carried the KRT9 missense mutations p.Arg163Trp and p.Arg163Gln, and successfully helped two families to bear normal daughters. We suggest that before the successful application of preimplantation genetic diagnosis (PGD), and noninvasive prenatal diagnosis of EPPK that analyzes fetal cells or cell-free DNA in maternal blood, prenatal genetic diagnosis by amniocentesis or chorionic villus sampling (CVS) offers a quite acceptable option for EPPK couples-at-risk to avoid the birth of affected offspring, especially in low- and middle-income countries.     

A new partial trisomy 12p with artery catheter vagus, congenital cataracts, external auditory canal, and no turbinate

We describe the prenatal diagnosis and fetal phenotype of partial trisomy 12 (p12-pter) transmitted from a maternal reciprocal translocation 6;12. Genetic analysis was conducted on umbilical cord blood for a fetus accompanied with tricuspid regurgitation and orbital hypertelorism from a 27-year-old gravida 4, para 1 after sonography at gestation 35weeks. The karyotype was unusual, with 46, XY, der (6), t (6;12) (p24; p12) mat. The pregnancy was terminated at 37 gestational weeks. The aborted fetus displayed dysmorphic features of a round flat face with prominent cheeks and high forehead, hypertelorism, short nose, broad and depressed nasal bridge, anteverted nares, deformed philtrum, open mouth, thin upper vermilion and broad everted lower lip, low-set ears and aural atresia, broad hands with simian creases, and a short neck. Fetal anatomy showed right artery catheter vagus, congenital cataract, no turbinate and external auditory canals. Through karyotype-phenotype analysis of this patient and a review of other reported cases, we believe this is a first report that expands the database of partial trisomy 12p, and is beneficial for future clinical genetic counseling. This study supports that phenotypic variability depends on the type and extent of the associated partial monosomy.     

Cri-du-chat (5p-) syndrome presenting with cerebellar hypoplasia and hypospadias: Prenatal diagnosis and aCGH characterization using uncultured amniocytes

We present prenatal diagnosis of a de novo distal deletion involving 5p(5p15.1 → pter) using uncultured amniocytes in a pregnancy with cerebellar hypoplasia, hypospadias and facial dysmorphisms in the fetus. We discuss the genotype–phenotype correlation and the consequence of haploinsufficiency of CTNND2, SEMA5A, TERT, SRD5A1 and TPPP. We speculate that haploinsufficiency of SRD5A1 and TPPP may be responsible for hypospadias and cerebellar hypoplasia, respectively, in this case.     

Mosaic small supernumerary marker chromosome 1 at amniocentesis: Prenatal diagnosis,molecular genetic analysis and literature review

We present prenatal diagnosis and molecular cytogenetic analysis of mosaic small supernumerary marker chromosome 1 [sSMC(1)]. We review the literature of sSMC(1) at amniocentesis and chromosome 1p21.1-p12 duplication syndrome. We discuss the genotype–phenotype correlation of the involved genes of ALX3, RBM15, NTNG1, SLC25A24, GPSM2, TBX15 and NOTCH2 in this case.     

Prenatal diagnosis of Pallister-Killian syndrome and literature review

Pallister-Killian syndrome (PKS) is a rare sporadic genetic disorder usually caused by mosaicism of an extra isochromosome of 12p (i(12p)). This retrospective study analysed the prenatal ultrasound manifestations and molecular and cytogenetic results of five PKS foetuses. Samples of amniotic fluid and/or cord blood, skin biopsy and placenta were collected. Conventional karyotyping and single nucleotide polymorphism array (SNP array) were performed on all the amniotic fluid or cord blood samples. Copy number variants sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) were also used for the validation for one foetus. All the five foetuses were from pregnancies with advanced parental age. Two foetuses involved structural abnormalities and one foetus had only soft markers, all of which included increased nuchal translucency. The rest two foetuses had normal ultrasounds in the second trimester, which has rarely been reported before. The karyotype revealed typical i(12p) in four cases and a small supernumerary marker chromosome consisting of 12p and 20p in the remaining one case. The proportion of cells with i(12p) ranged from 0 to 100% in cultural cells, while SNP array results suggested 2−4 copies of 12p. For one foetus, metaphase FISH showed normal results, but the interphase FISH suggested cell lines with two, three and four copies of 12p in the amniotic fluid. Advanced parental age may be an important risk factor for PKS, and there were no typical ultrasound manifestations related to PKS. A combination of karyotype analysis and molecular diagnosis is an effective method for the diagnosis of PKS.     

The second to fourth digit ratio and variation in the androgen receptor gene

The second to fourth digit ratio (2D:4D) is sexually dimorphic, with lower mean values in males compared to females. It has been suggested that the sex difference in 2D:4D is determined prenatally, 2D:4D is negatively related to prenatal testosterone and positively to prenatal oestrogen, and that 2D:4D is a marker for levels of sex steroids during brain organisation. There is growing evidence that many sex-dependent behaviours are correlated with 2D:4D. However, there is no direct evidence for an effect of prenatal sex steroids on the digit ratio. The response to prenatal testosterone is dependent on the amount produced and the foetal sensitivity to the hormone. Variation in the X-linked androgen receptor gene (AR) determines sensitivity to testosterone. Alleles of AR with low numbers of CAG triplets respond to testosterone with high transactivational activity, while high numbers of CAG's are associated with increased insensitivity to testosterone. We show in a sample of 50 men (49 Caucasian subjects, 1 Caucasian/Chinese subject) that 2D:4D is a phenotypic correlate of AR structure. Right-hand 2D:4D was positively correlated with CAG number and individuals with low 2D:4D in their right hand compared to left hand had AR alleles with low CAG numbers. We discuss the implications of our findings for our understanding of the aetiology of 2D:4D, its relationships with sex-dependent behaviours, and the evolutionary implications of variation in 2D:4D and AR.     

DNA sequences flanking an E. coli insertion element IS2 in a cloned yeast TRP5 gene

The insertion of an Escherichia coli IS2 element upstream from a cloned yeast TRP5 gene results in an increased level of active tryptophan synthase in trpAB E. coli host cells. This insertion occurs about 60 bp upstream from the first AUG of the TRP5 gene and is associated with a duplication of the sequence TTACA at the target site. The nucleotide sequence corresponding to the first 173 amino acids of the yeast TRP5 gene has also been determined. The N-terminal region of the yeast tryptophan synthase includes areas of strong homology with the alpha-subunit of the corresponding E. coli enzyme. Sequences from the 5' untranslated region upstream from the TRP5 gene are compared to homologous areas of other yeast genes.     

C19orf12 mutation leads to a pallido-pyramidal syndrome

Pallido-pyramidal syndromes combine dystonia with or without parkinsonism and spasticity as part of a mixed neurodegenerative disorder. Several causative genes have been shown to lead to pallido-pyramidal syndromes, including FBXO7, ATP13A2, PLA2G6, PRKN and SPG11. Among these, ATP13A2 and PLA2G6 are inconsistently associated with brain iron deposition. Using homozygosity mapping and direct sequencing in a multiplex consanguineous Saudi Arabian family with a pallido-pyramidal syndrome, iron deposition and cerebellar atrophy, we identified a homozygous p.G53R mutation in C19orf12. Our findings add to the phenotypic spectrum associated with C19orf12 mutations.