Trisomy 9 Mosaicism Diagnosed In Utero

We present three cases of trisomy 9 mosaicism diagnosed by amniocentesis with ongoing pregnancies after referral to our center due to fetal abnormalities. Two cases were associated with severe fetal growth restriction (FGR), each of which resulted in an intrauterine fetal demise (IUFD) in the third trimester. The other case involved mild FGR with a congenital diaphragmatic hernia and resulted in a live birth with severe development delay. A major prenatal finding of trisomy 9 mosaicism is FGR. Fetuses with trisomy 9 mosaicism can rarely survive in the case of severe FGR

Mutations in SERPINB7, Encoding a Member of the Serine Protease Inhibitor Superfamily, Cause Nagashima-type Palmoplantar Keratosis

“Nagashima-type” palmoplantar keratosis (NPPK) is an autosomal recessive nonsyndromic diffuse palmoplantar keratosis characterized by well-demarcated diffuse hyperkeratosis with redness, expanding on to the dorsal surfaces of the palms and feet and the Achilles tendon area. Hyperkeratosis in NPPK is mild and nonprogressive, differentiating NPPK clinically from Mal de Meleda. We performed whole-exome and/or Sanger sequencing analyses of 13 unrelated NPPK individuals and identified biallelic putative loss-of-function mutations in SERPINB7, which encodes a cytoplasmic member of the serine protease inhibitor superfamily. We identified a major causative mutation of c.796C>T (p.Arg266∗) as a founder mutation in Japanese and Chinese populations. SERPINB7 was specifically present in the cytoplasm of the stratum granulosum and the stratum corneum (SC) of the epidermis. All of the identified mutants are predicted to cause premature termination upstream of the reactive site, which inhibits the proteases, suggesting a complete loss of the protease inhibitory activity of SERPINB7 in NPPK skin. On exposure of NPPK lesional skin to water, we observed a whitish spongy change in the SC, suggesting enhanced water permeation into the SC due to overactivation of proteases and a resultant loss of integrity of the SC structure. These findings provide an important framework for developing pathogenesis-based therapies for NPPK

Imprinting of Human GRB10 and Its Mutations in Two Patients with Russell-Silver Syndrome

Documentation of maternal uniparental disomy of chromosome 7 in 10% of patients with Russell-Silver syndrome (RSS), characterized by prenatal and postnatal growth retardation and dysmorphic features, has suggested the presence of an imprinted gene on chromosome 7 whose mutation is responsible for the RSS phenotype. Human GRB10 on chromosome 7, a homologue of the mouse imprinted gene Grb10, is a candidate, because GRB10 has a suppressive effect on growth, through its interaction with either the IGF-I receptor or the GH receptor, and two patients with RSS were shown to have a maternally derived duplication of 7p11-p13, encompassing GRB10. In the present study, we first demonstrated that the GRB10 gene is also monoallelically expressed in human fetal brain tissues and is transcribed from the maternally derived allele in somatic-cell hybrids. Hence, human GRB10 is imprinted. A mutation analysis of GRB10 in 58 unrelated patients with RSS identified, within the N-terminal domain of the protein, a P95S substitution in two patients with RSS. In these two cases, the mutant allele was inherited from the mother. The fact that monoallelic GRB10 expression was observed from the maternal allele in this study suggests but does not prove that these maternally transmitted mutant alleles contribute to the RSS phenotype

An Alu retrotransposition-mediated deletion of CHD7 in a patient with CHARGE syndrome

CHD7 mutations account for about 60–65% among more than 200 CHARGE syndrome cases. When rare whole gene deletion cases associated with chromosomal abnormalities are excluded, all mutations of CHD7 reported to date have been point mutations and small deletions and insertions, rather than exonic deletions. To test whether exonic deletions represent a common pathogenic mechanism, we assessed exon copy number by using a recently developed method, the multiplex PCR/liquid chromatography assay (MP/LC). Multiple exons were amplified using unlabeled primers, then separated by ion-pair reversed-phase high-performance liquid chromatography, and quantitated by fluorescence detection using a post-column intercalation dye under the premise that the relative peak intensities for each target directly reflect exon copy number. By using MP/LC, we identified one CHARGE syndrome patient who had a de novo deletion encompassing exons 8–12 among 13 classic CHARGE patients in whom screening by denaturing high-performance liquid chromatography (DHPLC) failed to identify point mutations and small insertions/deletions in CHD7. This is the first CHARGE patient who was documented to have exonic deletion of CHD7. The deletion closely recapitulated the Alu-mediated inactivation of the human CMP-N-acetylneuraminic acid hydroxylase gene (CMP-Neu5Ac hydroxylase), which is regarded as a novel molecular mechanism in the evolution from non-human primates to humans. As demonstrated in this study, MP/LC is a promising method for characterizing exonic deletions, which are largely left unexamined in most routine mutation analysis