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  • Title: Sex-specific localization of laminin alpha 5 chain in the differentiating rat testis and ovary.
    Author: Fröjdman K, Miner JH, Sanes JR, Pelliniemi LJ, Virtanen I.
    Journal: Differentiation; 1999 Mar; 64(3):151-9. PubMed ID: 10234812.
    Abstract:
    The localization of laminin (Ln) alpha 5, beta 1 and beta 2 chains in the differentiating rat testis and ovary was studied by immunolabeling light and electron microscopy. The initial formation of the male and female gonadal blastemas included an emergence of Ln alpha 5 and beta 1 chains, but not of Ln beta 2 chain. The sexual differentiation of the embryonic male gonadal cords included rapid sex-specific disappearance of the incipient Ln alpha 5 chain. The rete testis cords, in contrast, remained positive for Ln alpha 5 chain. In the postnatal testis, the Ln alpha 5 chain reappeared in Ln beta 1 chain-positive cord basement membranes, which also became positive for Ln beta 2 chain. The differentiating myoid cells also gradually became positive for both Ln alpha 5 and Ln beta 1 chains. In the ovary Ln alpha 5 chain persisted in BMs of the cords throughout the fetal phase. Small and newly formed follicles in the early postnatal rat ovary were also positive for Ln alpha 5 chain, whereas growing and large follicles were negative. During the early postnatal phase, Ln beta 1-chain positive follicular BMs became also positive for the Ln beta 2 chain. Basement membranes of testicular and ovarian surface epithelia contained the Ln alpha 5 chain throughout the study. The blood vessels of the male and female gonad showed differentiation-dependent variation in their reactivity for the Ln alpha 5 and beta 2 chains. The present results show that the Ln alpha 5 chain is an early molecular marker for sexual differentiation, which therefore may be regulated by the testis-determining factors. The results also show that in the early postnatal rat ovary, the follicular basement membranes are heterogeneous in their Ln content, which may offer a means to distinguish different follicular populations from each other and to identify the different stages of follicular growth.
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