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.

Aim The purpose of this study was to report the 3‐year experience of a nationwide demonstration project to introduce non‐invasive prenatal testing (NIPT) of maternal plasma for aneuploidy, and review the current status of NIPT in Japan. Methods Tests were conducted to detect aneuploidy in high‐risk pregnant women, and adequate genetic counseling was provided. The clinical data, test results, and pregnancy outcomes were recorded. We discuss the problems of NIPT on the basis of published reports and meta‐analyses. Results From April 2013 to March 2016, 30 613 tests were conducted at 55 medical sites participating in a multicenter clinical study. Among the 30 613 women tested, 554 were positive (1.81%) and 30 021 were negative (98.1%) for aneuploidy. Of the 289, 128, and 44 women who tested positive for trisomies 21, 18, and 13, respectively, and underwent definitive testing, 279 (96.5%), 106 (82.8%), and 28 (63.6%) were determined to have a true‐positive result. For the 13 481 women with negative result and whose progress could be traced, two had a false‐negative result (0.02%). The tests were performed on the condition that a standard level of genetic counseling be provided at hospitals. Conclusion Here, we report on the 3‐year nationwide experience with NIPT in Japan. It is important to establish a genetic counseling system to enable women to make informed decisions regarding prenatal testing. Moreover, a welfare system is warranted to support women who decide to give birth to and raise children with chromosomal diseases.

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.

The 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.

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