Protein-Tyrosine Phosphatase, Receptor-Type, Q

Alternative Names

  • PTPRQ
  • Protein-tyrosine Phosphatase, Receptor-Type, Expressed by Glomerular Mesangial Cells 1
  • PTPGMC1
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OMIM Number

603317

Gene Map Locus
12q21.2

Description

PTPRQ belongs to the type III receptor-like protein-tyrosine phosphatase (PTPase) family. PTPRQ has low activity against phosphotyrosine, but is active against phosphatidylinositol phosphates that are involved in regulation of survival, proliferation, and subcellular architecture.

Molecular Genetics

The PTPRQ gene is located on the long arm of chromosome 12 at 12q21.2 and consists of 58 exons. The PTPRQ protein includes 2332 amino acids and weights around 261 kDa. It includes an extracellular domain containing 18 fibronectin III (FNIII) repeats, a membrane spanning domain, and a cytoplasmic domain with phosphatidylinositol phosphatase activity. Mutations in the PTPRQ gene are found to cause autosomal recessive nonsyndromic hearing loss.

Epidemiology in the Arab World

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Other Reports

Morocco

In two Moroccan male sibs, born to consanguineous parents, with autosomal recessive non-syndromic hearing loss with vestibular dysfunction (DFNB84), Schraders et al. (2010) identified a homozygous c.1369A>G transition in exon 19 of the PTPRQ gene, resulting in an arg457-to-gly (R457G) substitution in a highly conserved residue in the fifth FN3 domain, which is an extracellular domain known to bind ligands. The nomenclature of the mutation was based on splice variant III. The mutation was not found in 125 ethnically matched controls. Schraders et al. (2010) found that the phenotype was slightly less severe for the Moroccan family than that observed in a Dutch family, investigated also in this study, with a truncating mutation (Y497X), suggesting that the R457G mutant retains residual function.

Palestine

Shahin et al. (2010a) carried out a molecular study to identify the genes responsible for inherited hearing loss, by using high-density SNP arrays to genotype the DNA of 155 relatives (including: 78 patients, 28 of their hearing siblings, and 49 parents) from 20 Palestinian consanguineous families with prelingual bilateral autosomal recessive non-syndromic hearing loss (NSHL). Shahin et al. (2010a) found in two families linkage to a 12.5-Mb region on chromosome 12q (lod score of 3.45), designated DFNB84. No genes for inherited hearing loss have been described in this genomic region and it, therefore, represents a novel locus for recessive NSHL. Later, Shahin et al. (2010b) found out that these two families originated from the same extended kindred. In deaf and hearing relatives in this kindred, Shahin et al. (2010b) characterized genomically candidate genes in the 12.5 MB homozygous region, including the protein tyrosine phosphatase receptor Q (PTPRQ) gene, which is known to be essential to hearing in mouse. Sequencing of the PTPRQ gene in affected individuals revealed the presence of the c.1285C>T mutation, leading to p.Gln429Stop. This nonsense mutation was found to be co-segregated with hearing loss in the kindred and was found in homozygous state in all affected relatives. Shahin et al. (2010b) did not find the mutation among 288 Palestinian controls (576 chromosomes) and all adults with normal hearing. No homozygous mutations in PTPRQ appeared in any of 218 other probands with hearing loss. Shahin et al. (2010b) concluded that identification of the DFNB84 gene represents the first identification of PTPRQ mutation in human hearing loss.

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