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Abstract

Rab8B GTPase and junction dynamics in the testis (HTML) 
Lau,Ann S.N.; Mruk,Dolores D.
Endocrinology 144(4): 1549-1563
Publication date: 2003

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Throughout spermatogenesis, germ cells migrate from the basalto the adluminal compartment while remaining attached to Sertolicells via actin-based adherens and intermediate filament-basedanchoring junctions. However, the events that trigger deadhesionand adhesion remain largely unknown. As part of our continuedeffort in elucidating the mechanism of germ cell movement, wehave examined the role of Rab8B, a GTPase probably participatingin intracellular trafficking events at the site of the adherensjunction. By RT-PCR Rab8B mRNA was found in the brain, testis,heart, kidney, and spleen. Immunohistochemical studies revealedthat Rab8B was concentrated predominantly in the basal compartment,localizing to a similar site at which immunoreactive E-cadherinwas found. Additional experiments demonstrated that Rab8B associatedwith the actin, intermediate filament, and microtubule cytoskeletalnetworks. When Sertoli cells were cultured at high density orgerm cells were cocultured with Sertoli cells, Rab8B increasedsignificantly during junction assembly. Moreover, inclusionof germ cell-conditioned medium in Sertoli cell cultures resultedin stimulation of Rab8B expression. Conversely, treatment ofadult rats with 1-(2,4-dichlorobenzyl)-indazole-3-carbohydrazidereduced Rab8B mRNA and protein levels, coinciding with the timeof germ cell loss from the epithelium. Taken collectively, thesestudies suggest that Rab8B participates in adherens junctiondynamics in the testis.

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