Using degenerate PCR to identify novel PTPases expressed in glomerular mesangial cells from rats with experimentally-induced glomerulonephritis, Wright et al. (1998) cloned Ptprq, which they called Ptpgmc1. The Ptpgmc1 protein contains a signal peptide, 18 fibronectin (135600) type III-like adhesion domains, a transmembrane domain, and a single cytosolic PTPase domain. It also has putative sites for phosphorylation and N-linked glycosylation. Wright et al. (1998) also cloned a human partial PTPGMC1 cDNA. Northern blot analysis of rat tissues demonstrated Ptpgmc1 expression only in proliferating mesangial cells.

Seifert et al. (2003) presented evidence that cytoplasmic and receptor-like forms of rat and human PTPRQ are produced by alternative splicing and the use of alternative promoters. Northern blot analysis detected PTPRQ transcripts of 1.8 to 7.5 kb in human tissues and rat mesangial cells. The 1.8-kb transcript, which encodes a soluble protein containing only the catalytic domain, was predominant in human testis and rat mesangial cells, in which it was upregulated 7- to 8-fold following induction of glomerular injury. The 7.5-kb transcript, which encodes a protein containing both catalytic and extracellular domains, was predominant in human adult lung and adult and fetal kidney. In situ hybridization detected PTPRQ on the basal membrane of adult and fetal human glomerular podocytes, but not elsewhere in the kidney.

Schraders et al. (2010) reported complete characterization of the human PTPRQ gene and identified 4 different splice variants (I-IV). Alternative splicing occurred at the 5-prime end of the gene, and exon 49 was also alternatively spliced in both testes and retina. The splice variants differed in the number of FN3 domains, which are known to bind extracellular ligands, with variant I containing 2,200 amino acids and 15 FN3 domains, variant II containing 2,587 amino acids and 19 FN3 domains, variant III containing 2,517 amino acids and 19 FN3 domains, and variant IV containing 2,501 amino acids and 18 FN3 domains. Quantitative PCR analysis using a fragment encoding the intracellular region of PTPRQ detected expression in all but 2 human fetal tissues tested, with highest expression in fetal kidney, followed by fetal lung and fetal cochlea. Transcript levels were below detection level in fetal liver and fetal colon. In all adult human tissues tested, the highest transcript levels were in lung and heart.