Raghavan S S, Krusell A, Krusell J, Lyerla T A, Kolodny E H
Am J Hum Genet. 1985 Nov;37(6):1071-82.
To clarify the relationship between hexosaminidase A (HEX A) activity and GM2-ganglioside hydrolysis in atypical clinical situations of HEX A deficiency, we have developed a simple method to assess GM2-ganglioside metabolism in cultured fibroblasts utilizing GM2 labeled with tritium in the sphingosine portion of the molecule. The radioactive lipid is added to the media of cultured skin fibroblasts, and after 10 days the cells are thoroughly washed, then harvested, and their lipid composition analyzed by HPLC. The degree of hydrolysis of the ingested GM2 is determined by comparing the amount of radioactive counts recovered in undegraded substrate with total cellular radioactivity. A deficiency in GM2-ganglioside hydrolysis was demonstrated in seven HEX A-deficient adults with neurological signs and in two healthy-appearing adolescents with older affected siblings. In each case, an analysis of endogenous monosialoganglioside composition revealed an increase in GM2-ganglioside, confirming the presence of a block in the metabolism of GM2. No defect in GM2-catabolism was found in four other healthy individuals with HEX A deficiency. This method of assay is especially helpful in the evaluation of atypical cases of HEX A deficiency for the definitive diagnosis of GM2-gangliosidosis.
为了阐明在己糖胺酶A（HEX A）缺乏的非典型临床情况下己糖胺酶A活性与GM2神经节苷脂水解之间的关系，我们开发了一种简单的方法，利用分子中鞘氨醇部分用氚标记的GM2来评估培养的成纤维细胞中GM2神经节苷脂的代谢。将放射性脂质添加到培养的皮肤成纤维细胞培养基中，10天后将细胞彻底洗涤，然后收获，并通过高效液相色谱法分析其脂质组成。通过比较未降解底物中回收的放射性计数与总细胞放射性来确定摄入的GM2的水解程度。在7名有神经症状的HEX A缺乏成年患者和2名外表健康但有患病年长同胞的青少年中，证实存在GM2神经节苷脂水解缺陷。在每种情况下，对内源性单唾液酸神经节苷脂组成的分析显示GM2神经节苷脂增加，证实存在GM2代谢障碍。在其他4名HEX A缺乏的健康个体中未发现GM2分解代谢缺陷。这种检测方法在评估HEX A缺乏的非典型病例以明确诊断GM2神经节苷脂贮积症方面特别有用。
