Neurofibromatosis 2 (NF2) patients with constitutional splice site NF2 mutations have greater variability in disease severity than NF2 patients with other types of mutations; the cause of this variability is unknown. We evaluated genotype-phenotype correlations, with particular focus on the location of splice site mutations, using mutation and clinical information on 831 patients from 528 NF2 families with identified constitutional NF2 mutations. The clinical characteristics examined were age at onset of symptoms of NF2 and number of intracranial meningiomas, which are the primary indices of the severity of NF2. Two regression models were used to analyse genotype-phenotype correlations. People with splice site mutations in exons 1-5 had more severe disease than those with splice site mutations in exons 11-15. This result is compatible with studies showing that exons 2 and 3 are required for selfassociation of the amino terminal of the NF2 protein in vitro, and that deletions of exons 2 and 3 in transgenic and knockout mouse models of NF2 cause a high prevalence of Schwann cell derived tumours.

Autosomal-recessive cerebellar ataxias (ARCAs) are clinically and genetically heterogeneous disorders associated with diverse neurological and nonneurological features that occur before the age of 20. Currently, mutations in more than 20 genes have been identified, but approximately half of the ARCA patients remain genetically unresolved. In this report, we describe a Japanese family in which two siblings have slow progression of a type of ARCA with psychomotor retardation. Using whole-exome sequencing combined with homozygosity mapping, we identified a homozygous missense mutation in SYT14, encoding synaptotagmin XIV (SYT14). Expression analysis of the mRNA of SYT14 by a TaqMan assay confirmed that SYT14 mRNA was highly expressed in human fetal and adult brain tissue as well as in the mouse brain (especially in the cerebellum). In an in vitro overexpression system, the mutant SYT14 showed intracellular localization different from that of the wild-type. An immunohistochemical analysis clearly showed that SYT14 is specifically localized to Purkinje cells of the cerebellum in humans and mice. Synaptotagmins are associated with exocytosis of secretory vesicles (including synaptic vesicles), indicating that the alteration of the membrane-trafficking machinery by the SYT14 mutation may represent a distinct pathomechanism associated with human neurodegenerative disorders.

We describe a 5-year-old Japanese boy who has some radiographic findings characteristic of asphyxiating thoracic dystrophy (ATD)-chondroectodermal dysplasia with a de novo chromosome abnormality. He also has mild mental retardation, short stature, hypoplastic hair and skin, oligodontia, small thoracic cage, hypoplastic pelvis and cone-shaped epiphyses of hands. On cytogenetic studies he was found to have a de novo del(12)(p11.21p12.2). These results suggest that the locus of the gene associated with ATD-chondroectodermal dysplasia may be situated at 12p11.21p12.2.

Oral propranolol solution at 3 mg/kg/day is effective and safe in Japanese IH patients.

Cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS) is a late-onset, slow-progressing multisystem neurodegenerative disorder. Biallelic AAGGG repeat expansion in RFC1 has been identified as causative of this disease, and repeat conformation heterogeneity (ACAGG repeat) was also recently implied. To molecularly characterize this disease in Japanese patients with adult-onset ataxia, we accumulated and screened 212 candidate families by an integrated approach consisting of flanking PCR, repeat-primed PCR, Southern blotting and long-read sequencing using Sequel II, GridION or PromethION. We identified 16 patients from 11 families, of whom seven had ACAGG expansions [(ACAGG)exp/(ACAGG)exp] (ACAGG homozygotes), two had ACAGG and AAGGG expansions [(ACAGG)exp/(AAGGG)exp] (ACAGG/AAGGG compound heterozygotes) and seven had AAGGG expansions [(AAGGG)exp/(AAGGG)exp] (AAGGG homozygotes). The overall detection rate was 5.2% (11/212 families including one family having two expansion genotypes). Long-read sequencers revealed the entire sequence of both AAGGG and ACAGG repeat expansions at the nucleotide level of resolution. Clinical assessment and neuropathology results suggested that patients with ACAGG expansions have similar clinical features to previously reported patients with homozygous AAGGG expansions, although motor neuron involvement was more notable in patients with ACAGG expansions (even if one allele was involved). Furthermore, a later age of onset and slower clinical progression were implied in patients with ACAGG/AAGGG compound heterozygous expansions compared with either ACAGG or AAGGG homozygotes in our very limited cohort. Our study clearly shows the occurrence of repeat conformation heterogeneity, with possible different impacts on the affected nervous systems. The difference in disease onset and progression between compound heterozygotes and homozygotes might also be suspected but with very limited certainty due to the small sample number of cases in our study. Studies of additional patients are needed to confirm this.