A murine even-skipped homologue, Evx 1, is expressed during early embryogenesis and neurogenesis in a biphasic manner

Using the Drosophila even-skipped (eve) homeobox as a probe, we have isolated two murine genes, Evx 1 and Evx 2, from a genomic library. Evx 1, Evx 2, eve and the Xenopus Xhox-3 constitute a family of related genes based on similar homeodomain sequences. In addition, Evx 1 and Evx 2 share extended amino acid conservation outside of the homeobox. The Evx 1 protein consists of 416 amino acids as deduced from the longest open reading frame of Evx 1 cDNAs. Evx 1 is located 3.7 cM from the Hox 5 locus on mouse chromosome 2. It is expressed in undifferentiated F9 stem cells but not in cells differentiated with retinoic acid and cAMP. During embryogenesis, Evx 1 shows a biphasic expression pattern. From days 7 to 9 p.c. Evx 1 expression emerges at the posterior end of the embryo within the primitive ectoderm, and later in the mesoderm and neuroectoderm. From days 10 to 12.5 p.c. Evx 1 transcripts are restricted to specific cells within the neural tube and hindbrain along their entire lengths and coincides temporally, as well as spatially, with maturation of early forming interneurons, possibly commissural interneurons. The early and late transcription pattern is compatible with a role of Evx 1 in specifying posterior positional information along the embryonic axis similar to the Xenopus Xhox-3 and in specifying neuronal cell fates within the differentiating neural tube in analogy to eve in the embryonic central nervous system of Drosophila, respectively

Octamer binding proteins confer transcriptional activity in early mouse embryogenesis.

Oct4 and Oct5 are two mouse maternally expressed proteins binding to the octamer motif. Both are found in unfertilized oocytes and embryonic stem cells, whereas Oct4 is also found in primordial germ cells. In this study, the activity of the octamer motif was analysed in two embryonic stem cell lines containing Oct4 and Oct5, the teratocarcinoma-derived cell line F9 and the blastocyst-derived cell line D3. It is known that oligomerization of the octamer motif creates a powerful B-cell specific enhancer. As shown here, this oligomerized transcriptional element is also a very strong enhancer in F9 and D3 embryonic stem cells. After differentiation of the stem cells, both enhancer activity and the amount of the octamer binding proteins decrease. An intact octamer stimulates heterologous promoters in embryonic stem cells, whereas mutations in the octamer motif abolish transcriptional stimulation and binding of the octamer factors. The use of transgenic embryos demonstrates transcriptional activation in the inner cell mass but not in the trophoblast of blastocysts. The results indicate that Oct4 and Oct5 are active early in mouse development

A family of octamer-specific proteins present during mouse embryogenesis: Evidence for germline-specific expression of an Oct factor.

We have analysed various adult organs and different developmental stages of mouse embryos for the presence of octamer-binding proteins. A variety of new octamer-binding proteins were identified in addition to the previously described Oct1 and Oct2. Oct1 is ubiquitously present in murine tissues, in agreement with cell culture data. Although Oct2 has been described as a B-cell-specific protein, similar complexes were also found with extracts from brain, kidney, embryo and sperm. In embryo and brain at least two other proteins, Oct3 and Oct7, are present. A new microextraction procedure allowed the detection of two maternally expressed octamer-binding proteins, Oct4 and Oct5. Both proteins are present in unfertilized oocytes and embryonic stem cells, the latter containing an additional protein, Oct6. Whereas Oct4 was not found in sperm or testis, it is expressed in male and female primordial germ cells. Therefore Oct4 expression is specific for the female germline at later stages of germ cell development. Our results indicate that a family of octamer-binding proteins is present during mouse development and is differentially expressed during early embryogenesis. Protease clipping experiments of Oct4 and Oct1 suggest that both proteins contain similar DNA-binding domains

S-antigen and rod-opsin immunoreactions in midline brain neoplasms of transgenic mice: Similarities to pineal cell tumors and certain medulloblastomas in man.

Transgenic mice expressing the large T-antigen of the simian virus 40 (SV 40) under the control of 1) the enhancer of Moloney murine sarcoma virus (MSV) and 2) the SV 40 promoter develop undifferentiated neuroectodermal tumors located in the midline of the dorsal brain surface, abnormalities in lens fiber differentiation and retinal dysplasia. In this study the brain neoplasms of six adult animals and the brain of one 11-day old mouse were examined by conventional histology and immunocytochemical demonstration of S-antigen, rod-opsin, neuron-specific enolase, neurofilaments (160 and 200 kDa) and glial fibrillary acidic protein. According to histologic criteria the neoplasms were characterized as "primitive" neuroectodermal tumors composed mainly of small cells with scanty and ill-defined cytoplasm. Neoplastic cells displaying immunoreactive S-antigen were found in five brain tumors; three of these tumors also contained a limited number of rod-opsin immunoreactive neoplastic cells. Some tumor cells had neurite-like processes containing immunoreactive neurofilament (200 kDa). No pathologic lesions were found in the brain of the 11-day old animal. Tumors in transgenic mice may resemble pineal cell tumors and a special subtype of medulloblastoma in man. These neoplasms contain S-antigen immunoreactive and also rod-opsin immunoreactive tumors cells in certain cases. The findings suggest that transgenic mice expressing the large T-antigen of SV 40 may become a valuable animal model for analysing the origin, histogenesis and development of primitive neuroectodermal tumors with photoreceptor-like features (pineal cell tumors and certain medulloblastomas)

The catalytically inactive tyrosine phosphatase HD-PTP/PTPN23 is a novel regulator of SMN complex localization

The survival motor neuron (SMN) complex fulfils essential functions in the assembly of snRNPs, which are key components in the splicing of pre-mRNAs. Little is known about the regulation of SMN complex activity by posttranslational modification despite its complicated phosphorylation pattern. Several phosphatases had been implicated in the regulation of SMN, including the nuclear phosphatases PPM1G and PP1γ. Here we systematically screened all human phosphatase gene products for a regulatory role in the SMN complex. We used the accumulation of SMN in Cajal bodies of intact proliferating cells, which actively assemble snRNPs, as a readout for unperturbed SMN complex function. Knockdown of 29 protein phosphatases interfered with SMN accumulation in Cajal bodies, suggesting impaired SMN complex function, among those the catalytically inactive, non–receptor-type tyrosine phosphatase PTPN23/HD-PTP. Knockdown of PTPN23 also led to changes in the phosphorylation pattern of SMN without affecting the assembly of the SMN complex. We further show interaction between SMN and PTPN23 and document that PTPN23, like SMN, shuttles between nucleus and cytoplasm. Our data provide the first comprehensive screen for SMN complex regulators and establish a novel regulatory function of PTPN23 in maintaining a highly phosphorylated state of SMN, which is important for its proper function in snRNP assembly