Origin and specification of type II neuroblasts in the Drosophila embryo

Abstract

In , neural stem cells or neuroblasts (NBs) acquire different identities according to their site of origin in the embryonic neuroectoderm. Their identity determines the number of times they will divide and the types of daughter cells they will generate. All NBs divide asymmetrically, with type I NBs undergoing self-renewal and generating another cell that will divide only once more. By contrast, a small set of NBs in the larval brain, type II NBs, divides differently, undergoing self-renewal and generating an intermediate neural progenitor (INP) that continues to divide asymmetrically several more times, generating larger lineages. In this study, we have analysed the origin of type II NBs and how they are specified. Our results indicate that these cells originate in three distinct clusters in the dorsal protocerebrum during stage 12 of embryonic development. Moreover, it appears that their specification requires the combined action of EGFR signalling and the activity of the related genes and In addition, we also show that the INPs generated in the embryo enter quiescence at the end of embryogenesis, resuming proliferation during the larval stage.

In vivo analysis of the evolutionary conserved BTD-box domain of Sp1 and Btd during Drosophila development

“…The perdurance of the Cherry product also allows labeling most of the NB progeny as a Cherry-expressing cluster of cells. This wach genotype has been previously used successfully to identify type II NBs [20]. In wach wild type animals, we never observed expression of ase in type II NBs (Fig.…”

“…Therefore, we decided to study the requirement of this domain for other known functions executed by Sp1 and Btd. Besides their role during appendage development, btd controls the formation several head segments (intercalary, antennal and mandibular) [49], while both btd and Sp1 are required for type II NB identity specification [20]. First, we investigated the expression of Dll as a marker of the antennal segment and ventral thoracic primordia in btd ΔBTD-box / Df(btd, Sp1 ) mutant embryos.…”

“…Of these, only btd and Sp1 have been reported to be required for leg development [13, 17, 18]. These transcription factors also play important roles in Drosophila such as embryo head segmentation (only for btd ) and type II neuroblast (NB) specification and maintenance ( btd and Sp1 ) [5, 19, 20].…”

Genetic Mechanisms Regulating the Spatiotemporal Modulation of Proliferation Rate and Mode in Neural Progenitors and Daughter Cells during Embryonic CNS Development

“…In the brain hemisegments combined (B1-B3) about 106 NBs delaminate from the anterior neuroectoderm. Recently, another 8 NBs which divide in Type II mode (see below for division modes) have been identified in the embryonic brain [112,113], so in total there are 114 NBs in the B1-B3 hemisegments.…”

“…15). Embryonic Type II NBs have been recently identified in the brain and have been shown to contribute tremendously to the adult CNS [112,113].…”