O'Shea K S, Rheinheimer J S, O'Shea J M
Department of Anatomy and Cell Biology, University of Michigan, Ann Arbor.
J Craniofac Genet Dev Biol. 1987;7(4):357-69.
The early development of delayed Splotch mouse embryos was examined histologically using scanning electron microscopy and morphometric techniques. Embryos obtained from matings of mice heterozygous for the delayed Splotch gene exhibited a high incidence of lumbosacral (25%) or cephalic (7%) neural tube defects. The lumbosacral neural tube defects extended from the posterior neuropore region to the tip of the tailbud; cephalic neural tube closure defects were found in the hindbrain and midbrain regions. The frontal region of affected embryos was abnormal in that it was reduced in size, particularly in the developing midface. Histologically, the forebrain region of affected embryos appeared reduced, and the luminal surface of the neuroepithelium was often irregular and infolded. To quantify these alterations and to determine their contribution to the final form of the region, size and areal measurements were recorded and served as input for principal component and cluster analytic techniques. In affected embryos, significant reductions were found in lumen size, in neuroepithelial area but not thickness, and in overall area of forebrain but not hindbrain. Principal component analysis of data from unaffected embryos produced two factors, one containing hindbrain variables and the second forebrain variables; for the affected embryos, three factors were extracted. The first loaded on variables that measured the thickness and area of the neuroepithelium, the second on forebrain variables, and the third on hindbrain variables. Factor scores were then generated from a pooled analysis of normal and affected cases and were analyzed using cluster analysis. Three clusters were identified: one contained eight affected embryos with cephalic neural tube defects; another contained nine affected embryos with lumbosacral neural tube defects and five normal embryos; and the final cluster contained ten unaffected embryos. These results suggest a major role of the delayed Splotch gene on the neuroepithelium itself and support the suggested role of cerebrospinal fluid pressure in normal forebrain histogenesis.
利用扫描电子显微镜和形态测量技术对延迟斑点小鼠胚胎的早期发育进行了组织学检查。从携带延迟斑点基因杂合子的小鼠交配所获得的胚胎中，腰骶部（25%）或头部（7%）神经管缺陷的发生率很高。腰骶部神经管缺陷从后神经孔区域延伸至尾芽尖端；头部神经管闭合缺陷见于后脑和中脑区域。受影响胚胎的额部区域异常，其大小减小，尤其是在发育中的中面部。组织学上，受影响胚胎的前脑区域似乎变小，神经上皮的管腔表面通常不规则且有褶皱。为了量化这些改变并确定它们对该区域最终形态的影响，记录了大小和面积测量值，并将其作为主成分分析和聚类分析技术的输入数据。在受影响的胚胎中，发现管腔大小、神经上皮面积（但不是厚度）以及前脑总面积（但不是后脑）有显著减小。对未受影响胚胎的数据进行主成分分析产生了两个因子，一个包含后脑变量，另一个包含前脑变量；对于受影响的胚胎，提取了三个因子。第一个因子加载在测量神经上皮厚度和面积的变量上，第二个因子加载在前脑变量上，第三个因子加载在后脑变量上。然后通过对正常和受影响病例的汇总分析生成因子得分，并使用聚类分析进行分析。确定了三个聚类：一个包含八个有头部神经管缺陷的受影响胚胎；另一个包含九个有腰骶部神经管缺陷的受影响胚胎和五个正常胚胎；最后一个聚类包含十个未受影响的胚胎。这些结果表明延迟斑点基因对神经上皮本身有主要作用，并支持脑脊液压力在正常前脑组织发生中所起作用的观点。
