This gene encodes a member of the R3 subtype family of receptor-type protein tyrosine phosphatases. These proteins are localized to the apical surface of polarized cells and may have tissue-specific functions through activation of Src family kinases. This gene contains two distinct promoters, and alternatively spliced transcript variants encoding multiple isoforms have been observed. The encoded proteins may have multiple isoform-specific and tissue-specific functions, including the regulation of osteoclast production and activity, inhibition of cell proliferation and facilitation of apoptosis. This gene is a candidate tumor suppressor, and decreased expression of this gene has been observed in several types of cancer. [provided by RefSeq, May 2011].