Immunohistochemical expression and pathogenesis of BLM in the human brain and visceral organs

Bloom syndrome (BS) involves the clinical features of telangiectatic erythema, immunodeficiency, and an increased risk for cancer. In order to clarify the pathogenetic significance of the responsible gene, BLM, which encodes a protein possessing homology to Escherichia coli RecQ helicase, the immunohistochemistry of BLM was examined in human brains and visceral organs from fetuses to adults and an adult with BS, using anti-BLM antibodies. Purkinje cells exhibited positive BLM immunoreactivity from 21 gestational weeks (GW), which transiently increased at approximately 40 GW. Neurons of the pontine tegmentum were immunolabeled from the early fetal period. In visceral organs, positive BLM immunoreactivity was observed in the Hassal corpuscles in the thymus from 24 GW, in beta-cells in the Langerhans islets of the pancreas from 36 GW, and in sperm cells and sperms of the testes from 11 years of age. But in a patient with BS, it was negative in the pancreas and testis tissues examined. The characteristic effect of BLM on specific cells in different periods suggests that the BLM gene product is closely related to neuronal development as well as immune, insulin secretory and sperm functions, which appear in different periods, and disorders of which are major symptoms of BS.