Chicken oocytes and somatic cells express different splice variants of a multifunctional receptor.
An abundant 95-kDa protein belonging to the low density lipoprotein receptor supergene family is essential for chicken oocyte growth by mediating the uptake of multiple plasma-borne yolk precursors. This receptor harbors at the amino terminus a cluster of eight tandemly arranged repeats typical of the ligand binding domains of members of this family and is designated low density lipoprotein receptor relative with 8 repeats (LR8). Here, we demonstrate by reverse transcriptase-polymerase chain reaction, Northern, and Western blot analyses that the chicken expresses two forms of LR8, which are generated by differential splicing of an exon encoding a serine- and threonine-rich region characteristic of LRs, termed O-linked sugar domain. The female germ cell of the chicken expresses extremely high levels of the short form of LR8 (LR8-), i.e. the 95-kDa protein; in contrast, somatic cells express lower but detectable levels of the form containing the O-linked sugar domain (LR8+). The main sites of LR8+ expression in the chicken are the heart and skeletal muscle, i.e. the same tissues were LR8 mRNAs predominate in mammals; in addition, in situ hybridization demonstrates that a significant amount of LR8+ is produced in the hen's ovarian follicular granulosa cells. We found no apparent functional difference between the two receptor forms; however, cell type-specific targeting of the multiple ligands of these receptors possibly relates to their respective expression on the cell surface.
Bujo
H
H
Department of Molecular Genetics, Biocenter, Vienna, Austria.
Lindstedt
K A
KA
Hermann
M
M
Dalmau
L M
LM
Nimpf
J
J
Schneider
W J
WJ
D000818:Animals; D001483:Base Sequence; D002645:Chickens; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009865:Oocytes / Q000254:growth & development / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D011973:Receptors, LDL / Q000235:genetics* / Q000378:metabolism; D012091:Repetitive Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D011973:Receptors, LDL