The growth factor receptor tyrosine kinase family comprises several classes with distinct structural features. One class is represented by the ERBB family . A second
class includes dimeric receptors such as the insulin receptor as well as several protooncogenes. A third class of tyrosine kinase receptors is characterized by the presence of 5
immunoglobulin-like domains in the extracellular region and by the interruption of the catalytic domain in 2 parts by a
specific hydrophilic 'interkinase' sequence of variable length. This class includes the protooncogene FMS, which
encodes the CSF1 receptor, and KIT as well as 2 PDGF receptor genes and FLT1. A fourth class is represented by the
fibroblast growth factor receptors encoded by FLG (FLT2) and BEK. These receptors have strong
sequence similarities to the products of the third class but possess only 3 immunoglobulin-like domains in the
extracellular region and a short kinase insert in the intracellular domain. Rosnet et al. (1991) isolated a novel member
of the class 3 receptors. They demonstrated that this gene of the tyrosine kinase family, called FLT3, has strong
sequence similarities with other members of the group.
General function
Receptor, Enzyme, Transferase
Comment
Cellular localization
Plasma membrane
Comment
Ovarian function
Oogenesis, Oocyte maturation
Comment
Yoshinori Okamura et al 2001 reported the protein tyrosine kinase expression in the porcine ovary.
Various growth factor receptors contain intrinsic tyrosine kinase activity, indicating that protein tyrosine kinases (PTK)
play an important role in signal transduction pathways for cell proliferation and differentiation. To identify
oocyte-derived factors which control follicle cells as well as oocyte-controlling factors produced by follicle cells, the authors
examined the expression of genes which contain the PTK domain in the porcine ovary, using a polymerase chain
reaction-based amplification technique with degenerate oligonucleotide primers that are specific to the PTK domain.
Clones for the porcine
homologues of focal adhesion kinase (FAK), of c-kit and of fms-like tyrosine kinase (FLT)-3 were found only in
oocytes. Moreover, after 24 h of in-vitro maturation of the cumulus-oocyte complexes, clones for the porcine
homologues of FLT-1, of FLT-4, of Tie2 and of RYK in oocytes were observed. Immunohistochemical studies revealed
the existence of PDGFR, platelet-derived growth factor A (PDGFA), FAK and FLT3 in oocytes at various stages of
folliculogenesis. These results suggest that fluctuations in the expression of these PTK genes may be involved in follicle
growth and maturation.
Gene whose expression is detected by cDNA array hybridization: oncogenes, tumor
suppressors, cell cycle regulators Rozenn Dalbis-Tran and Pascal Mermilloda