Haruka Hamanoue

SMOC1 is essential for ocular and limb development in humans and mice.

Microphthalmia with limb anomalies (MLA) is a rare autosomal-recessive disorder, presenting with anophthalmia or microphthalmia and hand and/or foot malformation. We mapped the MLA locus to 14q24 and successfully identified three homozygous (one nonsense and two splice site) mutations in the SPARC (secreted protein acidic and rich in cysteine)-related modular calcium binding 1 (SMOC1) in three families. Smoc1 is expressed in the developing optic stalk, ventral optic cup, and limbs of mouse embryos. Smoc1 null mice recapitulated MLA phenotypes, including aplasia or hypoplasia of optic nerves, hypoplastic fibula and bowed tibia, and syndactyly in limbs. A thinned and irregular ganglion cell layer and atrophy of the anteroventral part of the retina were also observed. Soft tissue syndactyly, resulting from inhibited apoptosis, was related to disturbed expression of genes involved in BMP signaling in the interdigital mesenchyme. Our findings indicate that SMOC1/Smoc1 is essential for ocular and limb development in both humans and mice.

Rapid detection of a mutation causing X-linked leucoencephalopathy by exome sequencing

Background Conventional PCR-based direct sequencing of candidate genes for a family with X-linked leucoencephalopathy with unknown aetiology failed to identify any causative mutations. Objective To carry out exome sequencing of entire transcripts of the whole X chromosome to investigate a family with X linked leucoencephalopathy. Methods and results Next-generation sequencing of all the transcripts of the X chromosome, after liquid-based genome partitioning, was performed on one of the two affected male subjects (the proband) and an unaffected male subject (his brother). A nonsense mutation in MCT8 (c.1102A→T (p.R368X)) was identified in the proband. Subsequent PCR-based direct sequencing of other family members confirmed the presence of this mutation, hemizygous in the other affected brother and heterozygous in the probands mother and maternal grandmother. MCT8 mutations usually cause abnormal thyroid function in addition to neurological abnormalities, but this proband had normal thyroid function. Conclusion Single-lane exome next-generation sequencing is sufficient to fully analyse all the transcripts of the X chromosome. This method is particularly suitable for mutation screening of X-linked recessive disorders and can avoid biases in candidate gene choice.

Disrupted SOX10 Regulation of GJC2 Transcription Causes Pelizaeus-Merzbacher-Like Disease

Mutations in the gap junction protein gamma‐2 gene, GJC2, cause a central hypomyelinating disorder; Pelizaeus‐Merzbacher‐like disease (PMLD; MIM311601). Using a homozygosity mapping and positional candidate gene approach, we identified a homozygous mutation (c.‐167A>G) within the GJC2 promoter at a potent SOX10 binding site in a patient with mild PMLD. Functionally, this mutation completely abolished the SOX10 binding and attenuated GJC2 promoter activity. These findings suggest not only that the SOX10‐to‐GJC2 transcriptional dysregulation is a cause of PMLD, but also that GJC2 may be in part responsible for the central hypomyelination caused by SOX10 mutations. ANN NEUROL 2010;68:250–254

Genetic screening of 104 patients with congenitally malformed hearts revealed a fresh mutation of GATA4 in those with atrial septal defects

We analysed the GATA binding protein 4 gene, or GATA4, along with the NK2 transcription factor related, locus 5 gene, or NKX2.5, to determine their genetic contribution to 104 sporadic patients in Indonesia with congenitally malformed hearts, 76 cases having atrial septal defect and 28 tetralogy of Fallot. We found only 1 novel mutation of GATA4 in those with atrial septal defects. Analysis of the genetic background of the parents of the patient showed for the first time that a new mutation of GATA4 can cause sporadic atrial septal defects. We failed to discover any other mutations of either the GATA4 or NKX2-5 genes, supporting the marked genetic heterogeneity of human congenital cardiac defects.

A -16C>T substitution in the 5' UTR of the puratrophin-1 gene is prevalent in autosomal dominant cerebellar ataxia in Nagano.

AbstractThe molecular bases of autosomal dominant cerebellar ataxia (ADCA) have been increasingly elucidated, but 17-50% of ADCA families still remain genetically undefined in Japan. In this study we investigated 67 genetically undefined ADCA families from the Nagano prefecture, and found that 63 patients from 51 families possessed the −16C>T change in the puratrophin-1 gene, which was recently found to be pathogenic for 16q22-linked ADCA. Most patients shared a common haplotype around the puratrophin-1 gene. All patients with the −16C>T change had pure cerebellar ataxia with middle-aged or later onset. Only one patient in a large, −16C>T positive family did not have this change, but still shared a narrowed haplotype with, and was clinically indistinguishable from, the other affected family members. In Nagano, 16q22-linked ADCA appears to be much more prevalent than either SCA6 or dentatorubral-pallidoluysian atrophy (DRPLA), and may explain the high frequency of spinocerebellar ataxia.

Fetal cell-free DNA fraction in maternal plasma is affected by fetal trisomy.

The purpose of this noninvasive prenatal testing (NIPT) study was to compare the fetal fraction of singleton gestations by gestational age, maternal characteristics and chromosome-specific aneuploidies as indicated by z-scores. This study was a multicenter prospective cohort study. Test data were collected from women who underwent NIPT by the massively parallel sequencing method. We used sequencing-based fetal fraction calculations in which we estimated fetal DNA fraction by simply counting the number of reads aligned within specific autosomal regions and applying a weighting scheme derived from a multivariate model. Relationships between fetal fractions and gestational age, maternal weight and height, and z-scores for chromosomes 21, 18 and 13 were assessed. A total of 7740 pregnant women enrolled in the study, of which 6993 met the study criteria. As expected, fetal fraction was inversely correlated with maternal weight (P<0.001). The median fetal fraction of samples with euploid result (n=6850) and trisomy 21 (n=70) were 13.7% and 13.6%, respectively. In contrast, the median fetal fraction values for samples with trisomies 18 (n=35) and 13 (n=9) were 11.0% and 8.0%, respectively. The fetal fraction of samples with trisomy 21 NIPT result is comparable to that of samples with euploid result. However, the fetal fractions of samples with trisomies 13 and 18 are significantly lower compared with that of euploid result. We conclude that it may make detecting these two trisomies more challenging.

Whole-exome sequencing identified a homozygous FNBP4 mutation in a family with a condition similar to microphthalmia with limb anomalies

Microphthalmia with limb anomalies (MLA), also known as Waardenburg anophthalmia syndrome or ophthalmoacromelic syndrome, is a rare autosomal recessive disorder. Recently, we and others successfully identified SMOC1 as the causative gene for MLA. However, there are several MLA families without SMOC1 abnormality, suggesting locus heterogeneity in MLA. We aimed to identify a pathogenic mutation in one Lebanese family having an MLA‐like condition without SMOC1 mutation by whole‐exome sequencing (WES) combined with homozygosity mapping. A c.683C>T (p.Thr228Met) in FNBP4 was found as a primary candidate, drawing the attention that FNBP4 and SMOC1 may potentially modulate BMP signaling.

Breakpoint determination of X;autosome balanced translocations in four patients with premature ovarian failure.

Premature ovarian failure (POF) is a disorder characterized by amenorrhea and elevated serum gonadotropins before 40 years of age. As X chromosomal abnormalities are often recognized in POF patients, defects of X-linked gene may contribute to POF. Four cases of POF with t(X;autosome) were genetically analyzed. All the translocation breakpoints were determined at the nucleotide level. Interestingly, COL4A6 at Xq22.3 encoding collagen type IV alpha 6 was disrupted by the translocation in one case, but in the remaining three cases, breakpoints did not involve any X-linked genes. According to the breakpoint sequences, two translocations had microhomology of a few nucleotides and the other two showed insertion of 3–8 nucleotides with unknown origin, suggesting that non-homologous end-joining is related to the formation of all the translocations.

A locus for ophthalmo‐acromelic syndrome mapped to 10p11.23

Ophthalmo‐acromelic syndrome (OAS, OMIM %206920) is a rare autosomal recessive disease, presenting with clinical anophthalmia and limb anomalies. We recruited three OAS families including a Japanese family with two affected patients and two consanguineous Lebanese families each having an affected. Homozygosity mapping was performed using the 50K SNP chip and additional informative markers. A locus for OAS was mapped to the 422‐kb region at 10q11.23, based on the results from the two consanguineous families as well as the consistent data from the Japanese non‐consanguineous family. The 422‐kb region only contained one gene, MPP7. Although we could not detect any pathological mutations in OAS families analyzed, MPP7 could remain a candidate as aberrant changes might exist beyond our mutation detection methods. Further families are needed to confirm this candidate locus.

Complete hydatidiform mole and normal live birth following intracytoplasmic sperm injection

AbstractA twin pregnancy with complete hydatidiform mole (HM) and preterm birth of a normal female infant after intracytoplasmic sperm injection (ICSI) conception was experienced. ICSI due to severe oligozoospermia was performed on three ova, and three embryos with confirmed two proneclei (2PN) were subsequently transferred to the uterus. At 7 weeks of gestation, molar pregnancy as well as a viable fetus was recognized. At 33 weeks, the pregnancy was terminated due to preterm labor. Dichorionic pregnancy consisting of a normal fetus and placenta in one chorionic membrane and complete HM in the other was recognized. Cytomolecular analysis indicated that the complete HM genome was derived from duplication of a single sperm, and a normal neonate was from biparental genomes. It should be noted that ICSI can avoid incomplete HM (mostly triploid) due to multi-sperm fertilization but might not be able to avoid complete HM (paternal diploid) although such a risk is very low. This is the second report of this condition and is accompanied by the first well-described molecular analysis.