Biomedical subjects

H L Boettger-Tong

Publications and source records attributed to H L Boettger-Tong.

9 recordsLinked to original sources

PubMed2001

Identification and sequencing the juvenile spermatogonial depletion critical interval on mouse chromosome 1 reveals the presence of eight candidate genes.

In mice, the recessive, non-pleiotropic, juvenile spermatogonial depletion (jsd) mutation results in a single wave of spermatogenesis, followed by failure of type A spermatogonial stem cells to differentiate, rendering adult males sterile. As part of an effort to identify the gene underlying this mutation, we report here the construction of a high-resolution genetic map involving more than 1000 meioses and 24 polymorphic loci. Our data define a critical jsd interval of approximately 0.4 cM at 49 cM on mouse chromosome 1, between D1Mit215 and 257SP6. We have constructed a physical map spanning the region comprising 24 overlapping BACs. Eighteen of these BACs have been fully sequenced, or are in draft form, allowing us to annotate approximately 2.5 Mb of DNA surrounding the jsd locus. The critical 0.4 cM jsd interval corresponds to a physical distance of approximately 1.5 Mb. Eight genes have been identified in this interval, two of which appear to be possible candidates for the jsd mutation.

Animals↗

PubMed2001

A transgenic insertion causing cryptorchidism in mice.

A distinctive feature of gonadal maturation in mammals is the movement to an extraabdominal location. Testicular descent is a complex, multistage process whereby the embryonic gonads migrate from their initial abdominal position to the scrotum. Failure in this process results in cryptorchidism, a frequent congenital birth defect in humans. We report here a new mouse transgenic insertional mutation, cryptorchidism with white spotting (crsp). Males homozygous for crsp exhibit a high intraabdominal position of the testes, associated with complete sterility. Heterozygous males have a wild-type phenotype, and homozygous females are fertile. Surgically descended testes in crsp/crsp males show normal spermatogenesis. Using FISH and genetic analyses, the transgenic insert causing the crsp mutation has been mapped to the distal part of mouse chromosome 5. Transgene integration resulted in a 550-kb deletion located upstream of the Brca2 gene. A candidate gene encoding a novel G protein-coupled receptor (Great) with an expression pattern suggesting involvement in testicular descent has been identified.

Amino Acid Sequence↗

PubMed2000

Juvenile spermatogonial depletion (jsd) mutant seminiferous tubules are capable of supporting transplanted spermatogenesis.

In mice, the juvenile spermatogonial depletion (jsd) mutation results in a single wave of spermatogenesis followed by failure of type A spermatogonial stem cells to repopulate the testis, rendering male animals sterile. It is not clear whether the defect in jsd resides in a failure of the somatic component to support spermatogenesis or in a failure that is intrinsic to the mutant's germ cells. To determine if the jsd intratesticular environment is capable of supporting spermatogenesis, germ cell transplantation experiments were performed in which C57BL/6 ROSA germ cells were transplanted into jsd recipients. To determine if jsd spermatogonia are able to develop in a permissive seminiferous environment, jsd germ cells were transplanted into W/W(v) and busulfan-treated C57BL/6 animals. The data demonstrate that up to 7 mo after transplantation of normal germ cells, jsd seminiferous tubules are capable of supporting spermatogenesis. In contrast, when jsd germ cells were transplanted into busulfan-treated C57BL/6 testis, or into testis of W/W(v) mice, no jsd-derived spermatogenesis was observed. The data support the hypothesis that the jsd phenotype is due to a defect in the germ cells themselves, and not in the intratubular environment.

Animals↗

PubMed1998

Transposition of RhoA to the murine Y chromosome.

In an effort to produce a more complete transcription map of the short (approximately 5 Mb) arm of the mouse Y chromosome, we have initiated exon trapping from Yp-derived YACs. Sequence analysis of the trapped products has identified exons of previously cloned mouse Y-located genes Zfy and SSty and potential exons homologous to the human Y-located Tspy gene family. In addition, a family of three Yp-located transcripts that show close homology to human RHOA (locus designation ARHA), a member of the Ras family of small GTPases, has been identified. To determine whether these Yp sequences had been transposed from an autosomal ancestor, we used this trapped product to isolate a full-length autosomal mouse RhoA cDNA that is 80% identical at the nucleotide level and 98% identical at the amino acid level to human RHOA and maps to mouse Chromosome 2 (locus designation ArhA). Sequence analysis indicates that the Y-linked copies have diverged from the autosomal form, with small deletions precluding maintenance of a significant open reading frame in all Yp copies. Yet RT-PCR analysis indicates that two of these pseudogenes, RhoAy1 and 3, are expressed in a testis-specific manner, in sharp contrast to the nearly ubiquitous expression pattern of the autosomal ancestor. The data indicate that the Y copies of RhoA have been transposed from an autosome, followed by subsequent duplication, sequence divergence, and acquisition of a testis-specific promoter/enhancer.

Animals↗

PubMed1996

Uterine expression of vascular endothelial growth factor is increased by estradiol and tamoxifen.

Vascular endothelial growth factor (VEGF) is an endothelial-specific mitogen with potent angiogenic activity. Because vascular growth accompanies normal endometrial regeneration and may also be involved in uterine tumor growth, we studied VEGF regulation by 17 beta-estradiol (E2) and tamoxifen, two agents that can increase uterine cell proliferation and tumor incidence. In immature, ovariectomized rats, E2 elevates uterine VEGF mRNA transiently, with a peak induction of 15-20-fold within 1 h. A maximum response is produced at a dose of 4 micrograms/kg E2, and induction is specific for estrogenic steroids. E2-dependent VEGF induction is inhibited by actinomycin D but not puromycin, suggesting that the effect is due at least in part to direct estrogen receptor regulation of VEGF transcription. PCR amplification and DNA sequencing indicated that VEGF188, VEGF164, and VEGF120 are all induced by E2, but the latter two are the predominant forms in the uterus. In situ hybridization shows a predominantly stromal expression of VEGF mRNA. The antiestrogens tamoxifen, 4-OH tamoxifen, and nafoxidine produce similar increases in uterine VEGF mRNA levels within 6 h, with 1 mg/kg tamoxifen producing a maximum response of 15-20-fold. The tamoxifen response was also inhibited by actinomycin D but not by puromycin, again suggesting direct transcriptional regulation of VEGF expression by antiestrogens. These findings raise the possibility that estrogen and antiestrogen effects on uterine edema, proliferation, and tumor incidence may involve local increases in tissue VEGF production.

Animals↗

PubMed1995

Cellular pattern of c-fos induction by estradiol in the immature rat uterus.

Previous biochemical studies have shown that c-fos mRNA expression is rapidly and dramatically induced by estrogen in the immature rat uterus. In this work we have used in situ hybridization and immunocytochemistry to analyze the cellular pattern of proto-oncogene induction following administration of estradiol. The c-fos transcript and protein levels were low in control animals. Three hours after hormone treatment, the luminal and glandular epithelium, stroma, and myometrium all showed a clear increase in mRNA levels of the proto-oncogene as judged by in situ hybridization; this increase was most pronounced in the epithelial cells. Immunocytochemistry also demonstrated Fos expression in all cell layers with a higher fraction of cells staining in the epithelial and stromal layers than in the myometrium. Estradiol thus increased expression of c-fos in all major cell types of the immature uterus, although each tissue layer exhibited a specific pattern and degree of fos transcript and protein expression. This proto-oncogene is thus a marker for estrogen action in all uterine cell types at this stage of development. Since estrogen stimulates proliferation in all cell layers of the immature uterus, the cellular pattern of fos expression also correlates with the proliferative response to the hormone.

Animals↗

PubMed1995

Retinoic acid inhibits estrogen-induced uterine stromal and myometrial cell proliferation.

Retinoic acid, a potent natural derivative of vitamin A, influences proliferation in many cell types. However, little is known about the role of retinoic acid in estrogen-induced proliferation in normal physiological systems. In this study we sought to determine if in vivo administration of retinoic acid influences the proliferation of a normal estrogen target tissue, the immature rat uterus. The results indicate that treatment of animals with 30 mg/kg all-trans-retinoic acid for 3 days before 17 beta-estradiol (E2) administration diminishes DNA synthesis and cell division by approximately 50% in uterine stromal and myometrial cells. Luminal epithelial cell proliferation is not inhibited, indicating that the antiproliferative effects of all-trans-retinoic acid treatment are cell type-specific. The inhibition is retinoid-specific and fully reversible 1 week after discontinuing all-trans-retinoic acid treatment. The inhibitory effect of all-trans-retinoic acid is not due to a change in E2 receptor levels assessed by ligand binding. E2 induction of c-jun, a gene expressed primarily in myometrial cells, is unaffected in retinoid-treated animals. This is the first demonstration that retinoic acid inhibits estrogen-induced proliferation of uterine stromal and myometrial cells in a physiological setting.

Animals↗

PubMed1995

Toxicity of endogenous and environmental estrogens: what is the role of elemental interactions?

Many naturally occurring and man-made chemicals present in the environment possess estrogenic activity. Examples include plant and fungal products, pesticides, plasticizers, and other agricultural and industrial chemicals. These environmental estrogens as well as endogenous ovarian estrogens are thought to initiate their physiological actions in target tissues largely via interactions with a nuclear receptor system. The resultant estrogen-receptor complex in turn affects transcription via its interactions with nucleotide sequences known as estrogen response elements (EREs) present in the regulatory regions of hormone responsive genes. A "consensus" ERE sequence GGTCAnnnTGACC was originally identified in the vitellogenin genes of birds and amphibians, but it is now clear that most naturally occurring EREs differ from this sequence in one or more bases. We and others have obtained both in vivo and in vitro data suggesting a differential interaction of receptor complexes containing different ligands with the multiple EREs present in mammalian systems. This raises the possibility that the toxicity of environmental estrogens may arise in part from a differential pattern of ERE activation by environmental compounds relative to endogenous ovarian estrogens. The experimental basis for such a paradigm and its toxicological implications are discussed in this paper.

Animals↗

PubMed1993

Binding of a murine proteinase inhibitor to the acrosome region of the human sperm head.

Proteinase inhibitors are present in the various glands, tissues, and secretions of the male reproductive tract. Some of these inhibitors bind to the acrosomal region of the sperm, and their release during in vitro or in utero incubation suggests that they may play a role in capacitation. In the mouse, the binding site for a trypsin-acrosin inhibitor, the acceptor, has been implicated in capacitation, zona binding, and the acrosome reaction. This presentation demonstrates that a component, molecular weight approximately 20,000, on the human sperm head may recognize the murine inhibitor. Furthermore, the acrosome reaction can be induced in capacitated human sperm by immunoaggregation of bound murine inhibitor. The data indicate that the proteinase inhibitor binding site on the human sperm head may, as with a similar site on murine sperm, play a role in the early events of fertilization.

Acrosome↗