FXYD1 and neoplasm: The fourth gene cluster (g4) was specifically over-expressed in tumours of the h4 group and comprised 22 genes which were all found to be involved in nervous system development (e.g. ERBB3, GAS7, GPC3, SOX10), nervous system maintenance (e.g. ATP1A2, COL9A3, FXYD1), or associated to CNS in other ways (e.g. ASPA, CAPN3, MT2A, SERPINA3, SGPL1).