Polyadenylation, the process of eukaryotic mRNA 3 end formation, is essential for gene expression and cell viability. Polyadenylation of male germ cell mRNAs is unusual, exhibiting increased alternative polyadenylation, decreased AAUAAA polyadenylation signal use, and reduced downstream sequence element dependence. CstF-64, the RNA-binding component of the cleavage stimulation factor (CstF), interacts with pre-mRNAs at sequences downstream of the cleavage site. In mammalian testes, meiotic XY-body formation causes suppression of X-linked CstF-64 expression during pachynema. Consequently, an autosomal paralog, CstF-64 (gene name Cstf2t), is expressed during meiosis and subsequent haploid differentiation. Here we show that targeted disruption of Cstf2t in mice causes aberrant spermatogenesis, specifically disrupting meiotic and postmeiotic development, resulting in male infertility resembling oligoasthenoteratozoospermia. Furthermore, the Cstf2t mutant phenotype displays variable expressivity such that spermatozoa show a broad range of defects. The overall phenotype is consistent with a requirement for CstF-64 in spermatogenesis as indicated by the significant changes in expression of thousands of genes in testes of Cstf2t ؊/؊ mice as measured by microarray. Our results indicate that, although the infertility in Cstf2t ؊/؊ males is due to low sperm count, multiple genes controlling many aspects of germ-cell development depend on CstF-64 for their normal expression. Finally, these transgenic mice provide a model for the study of polyadenylation in an isolated in vivo system and highlight the role of a growing family of testis-expressed autosomal retroposed variants of X-linked genes.spermatogenesis ͉ oligoasthenoteratozoospemia ͉ meiosis ͉ XY body ͉ meiotic sex chromosome inactivation P olyadenylation, the process of mRNA 3Ј end formation, is required for the synthesis, transport, translation, and stability of eukaryotic mRNAs (1, 2). Although polyadenylation is nearly universal, features of polyadenylation are different in mammalian male germ cells than in other tissues: male germ cell mRNAs exhibit increased alternative polyadenylation (3, 4), decreased use of the AAUAAA polyadenylation signal (5, 6), and reduced dependence on downstream sequence elements (DSEs) (7). These differences suggest a modified mechanism for polyadenylation in male germ cells.While examining these differences, we discovered CstF-64 (8), which is a paralog of the 64,000 M r subunit of the cleavage stimulation factor (CstF-64) (9-11). CstF-64 is expressed in nuclei of early spermatogenic cells (5, 12). However, because it is on the X chromosome, CstF-64 expression halts in pachytene spermatocytes because of meiotic sex chromosome inactivation (MSCI) (13). In contrast, CstF-64 expression begins in pachytene spermatocytes and continues in spermatocytes and early spermatids (refs. 5 and 12; summarized in Fig. 1). CstF-64 is the only known CstF-64 homolog expressed during male meiosis, thus making it a candidate to play a critical role in sper...

A rapid expansion of new scientific information and the introduction of new technology in operative and diagnostic medicine has marked the last several decades. Medical educators, because of and parallel to these developments, initiated a search for a more effective system of presenting core material to medical students. The new educational trends, although varying somewhat from one institution to another, concentrated on the following pedagogical shifts: 1) expansion of conceptual presentation of material at the expense of detail-oriented education; 2) amplification of an integrated approach, as opposed to subject-oriented instruction; 3) scheduling of elective courses to compliment required courses in the curriculum; and 4) institution of small group instruction (i.e., problem-based learning) to actively involve students in the educational process and to develop deductive reasoning based on clinical cases. The future pedagogical system in medical schools will most likely be a combination of "classical" presentation of material combined with concept-oriented, subject-integrated and small group instruction based on either hypothetical or real clinical cases. It is imperative for the success of the new curriculum, however, that certain criteria are satisfied: 1) reorganize basic science departments to determine course ownership; 2) establish a reward system for teaching faculty; and 3) establish new course objectives.

Two beta-galactoside-binding proteins were isolated from uteroplacental complexes of pregnant mice and identified as the S-Lac lectins galectin-1 and galectin-3. The spatiotemporal pattern of appearance of those proteins was determined by immunocytochemistry. Galectin-1 was present in all tissue compartments of the uterus except the luminal and glandular epithelium. It was found in the uteri of animals from all preimplantation stages of pregnancy, as well as in those from nonpregnant, ovariectomized, or sexually immature animals. After implantation of the embryo, cells of the decidua basalis were labeled, as were granular metrial gland cells, all trophoblastic elements of the placenta, the myometrium, and nondecidualized endometrium. By contrast, there was little evidence of galectin-3 in the uteri of nonpregnant animals or during the preimplantation stages of pregnancy. However, immunoreactive material was observed in endometrial cells of the primary decidual zone immediately after implantation and at later stages of pregnancy in the decidua basalis, metrial gland, and all trophoblastic elements of the placenta. There was no evidence of galectin-3 in the myometrium or nondecidualized endometrium. After parturition, amounts of galectin-3 in the endometrium and metrial triangle appeared to decrease as the implantation sites were resorbed. These data suggested that the function of galectin-1 is one of tissue maintenance, whereas the function of galectin-3 is related specifically to pregnancy.