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Keywords:

  • osteogenesis imperfecta;
  • TMEM38B;
  • TRIC-B;
  • homozygosity mapping

ABSTRACT

Autosomal recessive osteogenesis imperfecta (OI) was diagnosed in three unrelated Israeli Bedouin consanguineous families. Fractures were evident in all cases in infancy. Genome-wide linkage analysis ruled out association with any of the known OI genes, and identified a single homozygosity locus of approximately 2 Mb on chromosome 9 common to all affected individuals (maximum multipoint lod score 6.5). Whole exome sequencing identified only a single mutation within this locus that was shared by all affected individuals: a homozygous deletion mutation of exon 4 of TMEM38B, leading to an early stop codon and a truncated protein, as well as low TMEM38B mRNA levels. TMEM38B encodes TRIC-B, a ubiquitous component of TRIC, a monovalent cation-specific channel involved in Ca2+ release from intracellular stores that has been shown to act in cell differentiation. Molecular mechanisms through which a TMEM38B mutation might lead to an OI phenotype are yet to be explored.