DEVELOPMENTAL-CHANGES IN SEMINIFEROUS TUBULE EXTRACELLULAR-MATRIX COMPONENTS OF THE MOUSE TESTIS - ALPHA-3(IV) COLLAGEN CHAIN EXPRESSED AT THE INITIATION OF SPERMATOGENESIS

The temporal expression of type IV collagen, laminin, and entactin in the basal laminae of the seminiferous tubule during development of the mouse testis was determined, Northern blot analysis was used to exami ne changes in testicular mRNA for alpha 1-alpha 5 type IV collagen (IV ) chains in mice ranging in age from newborn to adult (60 days). Level s for mRNA alpha 1(IV) and alpha 2(IV) chains were highest in newborns through Day 5 and remained elevated through Day 10, but then sharply declined to adult values by Day 30. In sharp contrast, alpha 3(IV) and alpha 4(IV) chain levels were low in newborns, peaked at Day 10, and then declined to adult values by Day 30. 5(IV) mRNA was elevated in ne wborns and at Days 5 and 10 before dropping to adult levels by Day 30. Changes in the deposition of alpha 1, alpha 2, and alpha 3(IV) collag en chains, laminin, and entactin into the inner and outer basal lamina e of the seminiferous tubule were determined from the beginning of tub ule formation (embryonic Day 12.5) through adulthood by immunofluoresc ence microscopy using polyclonal antibodies for these constituents, Th e alpha 1 and alpha 2(IV) chains, laminin, and entactin were deposited into the inner basal lamina at embryonic Day 12.5 and into the newly formed outer basal lamina at Day 5 after birth. The alpha 3(IV) chains were deposited into both the inner and outer basal laminae at Day 5. Thus, testicular alpha 1-alpha 3(IV) mRNA levels coincide with the inc orporation of detectable collagen chains into the seminiferous basal l aminae, suggesting transcriptional control of these alpha(IV) chains. Expression of the alpha 3(IV) chain coincides with the initiation of s permatogenesis, suggesting a functional role of this chain in spermato gonial proliferation.