Expression patterns of the hepatic leukemia factor gene in the nervous system of developing and adult mice

Hepatic leukemia factor (HLF) is a bZIP transcription factor related to the CES-2 protein, which controls apoptosis of the NSM serotoninergic neurons in Caenorhabditis elegans. Ectopic expression of HLF as an E2A-HLF fusion p rotein in t(17;19)-positive human pro-B cell acute lymphoblastic leukemias is believed to promote malignancy by interfering with apoptosis, While HLF has been linked to malignancies of the lymphoid system, it is not normally expressed in these cells. Rather, HLF transcripts are detected in the liver , kidney, lung and adult nervous system by Northern blotting. Despite the l inks to cell death, little is known of the distribution or function of HLF in the adult and developing mammalian nervous system. Therefore, we cloned mouse Hlf and studied its expression by in situ hybridization. During embry onic brain development, Hlf expression was restricted to the anterior pitui tary and meninges. By early postnatal life, Hlf was highly expressed in som atosensory cortex, thalamic nuclei, and structures arising from ectodermal placodes. Subsequently, Hlf expression increased in the central nervous sys tem and was found throughout the brain by adulthood. In the developing pitu itary gland, Hlf was highly expressed in the rostral tip of the anterior lo be. This pattern is similar to that of Tef, an Hlf-related bZIP protein. Ho wever, while Tef is expressed in the anterior pituitary of the adult mouse, Hlf was detected in both the anterior and posterior pituitary. Hlf express ion was not associated with cells undergoing programmed cell death in the n ervous system. Hlf expression increased markedly with synaptogenesis and wa s coincident with barrel formation revealed by cytochrome oxidase staining. Together, these data suggest that Hlf plays a role in the function of diff erentiated neurons in the adult nervous system rather than programmed cell death. (C) 1999 Published by Elsevier Science B.V. All rights reserved.