Disparate Tissue-specific Expression of Members of the Tissue Kallikrein Multigene Family of the Rat

Abstract

To understand the regulatory diversity of the rat family of linked kallikrein genes, we have assayed the expression of family members in 20 major organs. Reverse transcription-polymerase chain reaction analysis using primers and hybridization probes specific for each of the 10 expressed kallikrein genes showed that no two family members share the same organ-specific pattern of expression. The only common site of expression for all 10 known active genes is the submandibular gland. The presence of the mRNA for at least one family member is detected in 19 of these 20 organs (liver excepted), from as few as three organs to as many as 18 for individual family members. For individual genes there can be more than a 10 5 -fold variation in mRNA levels among organs, from a limit of detection of slightly less than 1 mRNA molecule/10 cells to more than 10,000 mRNA molecules/ cell. Despite high sequence conservation and close linkage, the members of this family are expressed in very different and complex patterns. A gradient of diversity of expression corresponds to the order of the genes within the kallikrein family locus.

An overview of the kallikrein gene families in humans and other species: emerging candidate tumour markers

“…Another large family of about 13 kallikreins was identified in the rat, of which at least 10 are transcriptionally active [18]. More recent data from the Rat Genome Database (http://ratmap.gen.gu.SE/) points to the possibility for more kallikreins in the rat genome.…”

A Genomic Analysis of Rat Proteases and Protease Inhibitors

“…We have annotated 23 kallikreins in rat, whereas there are 26 in mouse and 15 in human. These kallikreins can be divided into two groups according to their relative location within two closely linked clusters present at chromosomes 1q21 in rat, 7B2 in mouse, and 19q13 in human (MacDonald et al 1996;Yousef and Diamandis 2001;Olsson and Lundwall 2002). The first cluster contains 13 kallikrein genes in rat, 12 in mouse, and 15 in human.…”

Tissue-specific Expression Patterns and Fine Mapping of the Human Kallikrein (KLK) Locus on Proximal 19q13.4

“…Whereas KLK2 and KLK3 are primarily expressed at high levels in the secretory epithelium of the prostatic ducts and have been implicated in normal prostatic function as well as in cancer progression (8), tissue kallikrein, through its multifunctional roles, is involved in the (patho)physiology of the kidney, brain, and respiratory, gastrointestinal, and reproductive tracts (2). This diverse functionality is underscored by the ubiquitous expression pattern observed for KLK1 in the rat (9). Although a function has not yet been ascribed to the protein products of most other rat KLK genes, an indication of the tissue in which they will be functional is gained from their tissue expression patterns (9).…”

“…This diverse functionality is underscored by the ubiquitous expression pattern observed for KLK1 in the rat (9). Although a function has not yet been ascribed to the protein products of most other rat KLK genes, an indication of the tissue in which they will be functional is gained from their tissue expression patterns (9). In man, the newly identified KLK serine proteases, Protease M/neurosin/zyme (10 -12) and normal epithelial cell-specific 1 (Nes1) 2 (13), are highly ex-pressed in brain and breast tissue, and have been suggested to be involved in Alzheimer's disease and breast cancer, respectively (12)(13)(14).…”