Neuroscience Graduate Program, University of California San Francisco, San Francisco, CA, USA.
J Biomed Sci. 2010 Oct 17;17(1):82. doi: 10.1186/1423-0127-17-82.
Multicellular organisms are characterized by a remarkable diversity of morphologically distinct and functionally specialized cell types. Transgenic techniques for the manipulation of gene expression in specific cellular populations are highly useful for elucidating the development and function of these cellular populations. Given notable similarities in developmental gene expression between pancreatic β-cells and serotonergic neurons, we examined the pattern of Cre-mediated recombination in the nervous system of a widely used mouse line, Pdx1-cre (formal designation, Tg(Ipf1-cre)89.1Dam), in which the expression of Cre recombinase is driven by regulatory elements upstream of the pdx1 (pancreatic-duodenal homeobox 1) gene.
Single (hemizygous) transgenic mice of the pdx1-creCre/0 genotype were bred to single (hemizygous) transgenic reporter mice (Z/EG and rosa26R lines). Recombination pattern was examined in offspring using whole-mount and sectioned histological preparations at e9.5, e10.5, e11.5, e16.5 and adult developmental stages.
In addition to the previously reported pancreatic recombination, recombination in the developing nervous system and inner ear formation was observed. In the central nervous system, we observed a highly specific pattern of recombination in neuronal progenitors in the ventral brainstem and diencephalon. In the rostral brainstem (r1-r2), recombination occurred in newborn serotonergic neurons. In the caudal brainstem, recombination occurred in non-serotonergic cells. In the adult, this resulted in reporter expression in the vast majority of forebrain-projecting serotonergic neurons (located in the dorsal and median raphe nuclei) but in none of the spinal cord-projecting serotonergic neurons of the caudal raphe nuclei. In the adult caudal brainstem, reporter expression was widespread in the inferior olive nucleus. In the adult hypothalamus, recombination was observed in the arcuate nucleus and dorsomedial hypothalamus. Recombination was not observed in any other region of the central nervous system. Neuronal expression of endogenous pdx1 was not observed.
The Pdx1-cre mouse line, and the regulatory elements contained in the corresponding transgene, could be a valuable tool for targeted genetic manipulation of developing forebrain-projecting serotonergic neurons and several other unique neuronal sub-populations. These results suggest that investigators employing this mouse line for studies of pancreatic function should consider the possible contributions of central nervous system effects towards resulting phenotypes.
多细胞生物的特点是形态上明显不同和功能上专门化的细胞类型的多样性。用于在特定细胞群体中操纵基因表达的转基因技术对于阐明这些细胞群体的发育和功能非常有用。鉴于胰腺β细胞和 5-羟色胺能神经元在发育基因表达方面的显著相似性，我们研究了广泛使用的小鼠品系 Pdx1-cre（正式名称，Tg（Ipf1-cre）89.1Dam）中神经 系统中 Cre 介导的重组模式，其中 Cre 重组酶的表达由 pdx1（胰腺十二指肠同源盒 1）基因上游的调控元件驱动。
将 Pdx1-creCre/0 基因型的单（半合子）转基因小鼠与单（半合子）转基因报告小鼠（Z/EG 和 rosa26R 系）交配。在 e9.5、e10.5、e11.5、e16.5 和成年发育阶段，使用全组织和切片组织学制剂检查后代中的重组模式。
除了先前报道的胰腺重组外，还观察到发育中的神经系统和内耳形成中的重组。在中枢神经系统中，我们观察到腹侧脑干和间脑神经元祖细胞中高度特异性的重组模式。在颅干（r1-r2）中，新生 5-羟色胺能神经元中发生了重组。在脑干尾部，发生在非 5-羟色胺能细胞中。在成年期，这导致报告基因在绝大多数前脑投射 5-羟色胺能神经元（位于背侧和中缝核）中表达，但在尾状核中投射脊髓的 5-羟色胺能神经元中不表达。在成年尾状脑干中，报告基因在橄榄核下广泛表达。在成年下丘脑，观察到弓状核和下丘脑背内侧核的重组。在中枢神经系统的任何其他区域都没有观察到重组。内源性 pdx1 的神经元表达未观察到。
Pdx1-cre 小鼠品系和相应转基因中包含的调控元件可能是用于靶向遗传操纵前脑投射 5-羟色胺能神经元和其他几个独特神经元亚群的有价值的工具。这些结果表明，使用这种小鼠品系进行胰腺功能研究的研究人员应考虑中枢神经系统效应对表型产生的可能贡献。
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