RESUMO
To function properly, tissue-specific stem cells must reside in a niche. The Drosophila testis niche is one of few niches studied in vivo. Here, a single niche, comprising ten hub cells, maintains both germline stem cells (GSC) and somatic stem cells (CySC). Here, we show that lines is an essential CySC factor. Surprisingly, lines-depleted CySCs adopted several characteristics of hub cells, including the recruitment of new CySCs. This led us to examine the developmental relationship between CySCs and hub cells. In contrast to a previous report, we did not observe significant conversion of steady-state CySC progeny to hub fate. However, we found that these two cell types derive from a common precursor pool during gonadogenesis. Furthermore, lines mutant embryos exhibited gonads containing excess hub cells, indicating that lines represses hub cell fate during gonadogenesis. In many tissues, lines acts antagonistically to bowl, and we found that this is true for hub specification, establishing bowl as a positively acting factor in the development of the testis niche.
Assuntos
Proteínas de Transporte/fisiologia , Proteínas de Ligação a DNA/fisiologia , Proteínas de Drosophila/fisiologia , Drosophila/embriologia , Nicho de Células-Tronco , Testículo/citologia , Testículo/embriologia , Fatores de Transcrição/fisiologia , Animais , Animais Geneticamente Modificados , Padronização Corporal/genética , Proteínas de Transporte/genética , Desdiferenciação Celular/genética , Desdiferenciação Celular/fisiologia , Diferenciação Celular/genética , Diferenciação Celular/fisiologia , Proliferação de Células , Proteínas de Ligação a DNA/genética , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/genética , Embrião não Mamífero , Células Germinativas/citologia , Células Germinativas/metabolismo , Masculino , Testículo/metabolismo , Fatores de Transcrição/genéticaRESUMO
Community-based dental education programs such as externship programs have become an integral component of dental school education. Qualitative evaluation of externship programs has captured increased confidence, efficiency, skill, and independence among students. To better understand these findings, quantitative evaluation of the externship experience is necessary. The current study investigated the clinical care (defined as dental procedures) provided by Boston University School of Dental Medicine students who completed six-week general dentistry externships compared to those completing ten-week general dentistry externships. Results indicate that the scope of services provided in the ten-week externship differed from the six-week externship. The longer externships allowed for students to perform more complex procedures toward the latter part of their externships. Students participating in the ten-week externship also provided more procedures per week than students in the six-week externship. Because scheduling of patient appointments is generally a function of the site, number of patient visits and procedures performed per patient did not differ between the two groups. Our findings provide insight into the reason why longer externships increase clinical confidence, efficiency, and skill. In the continuing effort to improve the externship experience in dental schools, these findings should be taken into consideration.