Analysis of genes expressed during porcine fetal pituitary development by suppressive subtraction hybridization.

Pituitary organogenesis is modulated by temporal and special expression of various genes at the fetal stage. Suppressive subtraction cloning was employed to search for genes expressed during porcine fetal pituitary development. The variations in the genes expressed in the pituitaries on fetal days 40 and 110, respectively, were analyzed by subtraction with the inverted combination. Genes encoding growth arrest specific-2, coated vesicle membrane protein, steroid membrane binding protein, putative protease cancer tumor suppressor, secretogranin, calumenin and others exhibited elevated expression during pituitary development, in addition to genes encoding GH, prolactin and glycoprotein hormone common alpha subunit. Concomitantly, we also found a gene that encodes a porcine ortholog of c-myc transcription factor and determined its entire nucleic acid sequence. On the other hand, histone H3.3B, GTP-binding alpha-stimulatory subunit, stathmin and others were found as gene expression decreased. Thus, the expression levels of many genes change during pituitary development.

Prominent expression of spinocerebellar ataxia type-1 (SCA1) gene encoding ataxin-1 in LH-producing cells, LbetaT2.

The LH-producing cell line, LbetaT2, and non LH-producing cell line, alphaT3-1 cells, established from a pituitary tumor, were employed for cDNA subtraction cloning to identify genes with expression unique to LH producing cells. Several cDNAs that code for known as well as for many unidentified clones were discovered. Most clones were the spinocerebellar ataxia type-1 (SCA1) gene encoding ataxin-1, the abnormality of which causes neurodegeneration and loss of cerebellar Purkinje cells. We examined whether the expression of SCA1 gene in LbetaT2 cells is related to hormone production. We also compared the expression of SCA1 with that in various other pituitary tumor derived cell lines, and confirmed the prominent expression of SCA1 in LbetaT2 cells. The effect of gonadal factor(s) for SCA1 gene expression was examined. The expression level in female rats was low and did not change during the estrus cycle, but increased significantly after ovariectomy and did not return to the normal level under low and high doses of estrogen. In the male pituitary SCA1 gene expression increased markedly after castration and was not decreased by estrogen or testosterone. The Ontogeny of SCA1 gene expression was investigated in porcine fetal and postnatal pituitaries and revealed biphasic and sexually dimorphic expression. Transient expression of SCA1 gene was observed at fetal day 50 and 65 in males and day 40 in females, followed by a decline and increased expression before birth in both genders. Thus the expression of SCA1 gene is prominent in LH-producing cells and is not under direct control of gonadal factor(s) in both genders. In addition to the variable expression of SCA1 gene during the fetus period, the present results provide a novel aspect to the understanding of Boucher-Neuhauser syndrome (Ataxia Hypogonadism Choroidal Dystrophy).