Savage R M, Shankland M
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Dev Biol. 1996 May 1;175(2):205-17. doi: 10.1006/dbio.1996.0108.
Lzf1 and Lzf2 are leech zinc finger (Lzf) genes that are shown to be orthologues to the Drosophila gap gene hunchback (hb). Neither in situ hybridization nor RT-PCR detected Lzf1 transcripts in leech embryos or adults. Lzf2 expression was examined in leech embryos at various stages by in situ hybridization. Lzf2 is expressed continually throughout the early embryonic cleavage divisions, including the period during which the embryo forms stem cells that will give rise to the segmented tissues of the adult. At the time of segmental pattern formation, Lzf2 RNA is expressed uniformly along the length of the segmented trunk in both the ectodermal and mesodermal tissues. This is in contrast to the anteriorly restricted gradient of hb RNA shown to be critical to the normal anteroposterior (AP) patterning of the insect embryo. Thus, this leech orthologue of hb does not appear to play a comparable role in the patterning of the AP axis. In addition, Lzf2 is expressed during organogenesis in segmentally restricted patterns in the central nervous system, the gut, and epidermally derived structures. Lzf2 is the first hb orthologue to be characterized in detail outside of insects and its expression pattern suggests that hb may have acquired a gap gene function in arthropods or insects after their phyletic separation from the annelids.
Lzf1和Lzf2是水蛭锌指（Lzf）基因，已被证明是果蝇缺口基因驼背（hb）的直系同源基因。原位杂交和逆转录聚合酶链反应均未在水蛭胚胎或成体中检测到Lzf1转录本。通过原位杂交检测了水蛭胚胎不同阶段的Lzf2表达。Lzf2在整个早期胚胎分裂过程中持续表达，包括胚胎形成将产生成体节段组织的干细胞的时期。在节段模式形成时，Lzf2 RNA在外胚层和中胚层组织中沿节段化躯干的长度均匀表达。这与hb RNA在前部受限的梯度形成对比，后者对昆虫胚胎正常的前后（AP）模式形成至关重要。因此，这个水蛭的hb直系同源基因似乎在AP轴模式形成中不发挥类似作用。此外，Lzf2在器官发生过程中在中枢神经系统、肠道和表皮衍生结构中以节段受限模式表达。Lzf2是第一个在昆虫以外详细表征的hb直系同源基因，其表达模式表明hb可能在节肢动物或昆虫与环节动物在系统发育上分离后获得了缺口基因功能。
