Functional analysis of hmx-1 gene in the developing embryo

小鼠Hmx家族的三个基因，命名为Hmx 1、Hmx 2和Hmx 3，在感觉神经和子宫中表达，表明在这些器官的发育和/或怀孕中发挥功能作用。Hmx 3基因敲除小鼠的内耳结构异常，表现为纯合子小鼠的着床缺陷。为了分析Hmx 1基因在器官发育和妊娠中的功能，我们采用同源重组技术。Hmx 1基因的纯合性靶向破坏导致F1（129/Sv：C57 BL/6）杂合子互交在胚胎第6-7天死亡。但这种致死性在F2或F3杂交中被挽救。提示C57 BL/6小鼠基因组中可能存在拯救基因。然而，在目前的状态下，还不清楚母亲或胚胎的基因型是否可以挽救致命的表型。一旦纯合子小鼠发育超过E5-E7临界日期，它们甚至在表达Hmx 1的组织中也是完全正常的。

The three genes of the murine Hmx family, designated Hmx1, Hmx2, and Hmx3, are expressed in the sensory nerve and uterus that suggest a functional role in development of those organs and/or pregnancy. The Hmx3 knockout mice, as suspected by the expressed region, show abnormal structure of inner ear and implantation defect in homozygote mice. To analyze the function of Hmx1 gene in the organ development and pregnancy, we adopted the homologous recombination technique. Homozygous targeted disruption of Hmx1 gene result in lethality at embryonic day 6-7 in intercross of F1 (129/Sv : C57BL/6) heterozygote. But this lethality is rescued in F2 or F3 intercross. This phenomenon suggest that rescue gene may exist in C57BL/6 mice genome. In the present state, however, it is unclear whether the genotype of mother or embryo could rescue the lethal phenotye. Once homozygote mice develop beyond the E5-E7 critical date, they are completely normal even in the tissues in which Hmx1 is expressed.