The region of mouse mammary tumor virus DNA containing the long terminal repeat includes a long coding sequence and signals for hormonally regulated transcription.

Starting from a biologically active recombinant DNA clone of exogenous unintegrated GR mouse mammary tumor virus, we have generated three subclones of PstI fragments of 1.45, 1.1, and 2.0 kb in the plasmid vector PBR322. The nucleotide sequence has been determined for the clone of 1.45 kb which includes almost the complete region of the long terminal repeat (LTR) plus an adjacent stretch of unique sequence DNA. A short region of the 2.0 kb clone, containing the beginning of the LTR, has also been sequenced. Starting with the A of an initiation codon outside the LTR, we detected an open reading frame of 960 nucleotides, potentially coding for a protein of 320 amino acids (36K). Two hundred nucleotides downstream from the termination codon, and approximately 25 nucleotides upstream from the presumptive initiation site of viral RNA synthesis, we found a promoter-like sequence. The sequence AGTAAA was detected approximately 15-20 nucleotides upstream from the 3' end of virion RNA and probably serves as a polyadenylation signal. The 1.45 kb PstI fragment has been transfected into Ltk- cells together with a plasmid containing the thymidine kinase gene of herpes simplex virus. The virus-specific RNA synthesis detected in a Tk+ cell clone was strongly stimulated by the addition of dexamethasone.

Lethal skeletal dysplasia in mice and humans lacking the golgin GMAP-210.

BACKGROUND: Establishing the genetic basis of phenotypes such as skeletal dysplasia in model organisms can provide insights into biologic processes and their role in human disease. METHODS: We screened mutagenized mice and observed a neonatal lethal skeletal dysplasia with an autosomal recessive pattern of inheritance. Through genetic mapping and positional cloning, we identified the causative mutation. RESULTS: Affected mice had a nonsense mutation in the thyroid hormone receptor interactor 11 gene (Trip11), which encodes the Golgi microtubule-associated protein 210 (GMAP-210); the affected mice lacked this protein. Golgi architecture was disturbed in multiple tissues, including cartilage. Skeletal development was severely impaired, with chondrocytes showing swelling and stress in the endoplasmic reticulum, abnormal cellular differentiation, and increased cell death. Golgi-mediated glycosylation events were altered in fibroblasts and chondrocytes lacking GMAP-210, and these chondrocytes had intracellular accumulation of perlecan, an extracellular matrix protein, but not of type II collagen or aggrecan, two other extracellular matrix proteins. The similarities between the skeletal and cellular phenotypes in these mice and those in patients with achondrogenesis type 1A, a neonatal lethal form of skeletal dysplasia in humans, suggested that achondrogenesis type 1A may be caused by GMAP-210 deficiency. Sequence analysis revealed loss-of-function mutations in the 10 unrelated patients with achondrogenesis type 1A whom we studied. CONCLUSIONS: GMAP-210 is required for the efficient glycosylation and cellular transport of multiple proteins. The identification of a mutation affecting GMAP-210 in mice, and then in humans, as the cause of a lethal skeletal dysplasia underscores the value of screening for abnormal phenotypes in model organisms and identifying the causative mutations.

Functional expression of a pseudohypoaldosteronism type I mutated epithelial Na+ channel lacking the pore-forming region of its alpha subunit.

The autosomal recessive form of type I pseudohypoaldosteronism (PHA-I) is an inherited salt-losing syndrome resulting from diminution-of-function mutations in the 3 subunits of the epithelial Na+ channel (ENaC). A PHA-I stop mutation (alpha(R508stop)) of the ENaC alpha subunit is predicted to lack the second transmembrane domain and the intracellular COOH-terminus, regions of the protein involved in pore function. Nonetheless, we observed a measurable Na+ current in Xenopus laevis oocytes that coexpress the beta and gamma subunits with the truncated alpha subunit. The mutant alpha was coassembled with beta and gamma subunits and was present at the cell surface at a lower density, consistent with the lower Na+ current seen in oocytes with the truncated alpha subunit. The single-channel Na+ conductance for the mutant channel was only slightly decreased, and the appearance of the macroscopic currents was delayed by 48 hours with respect to wild-type. Our data suggest novel roles for the alpha subunit in the assembly and targeting of an active channel to the cell surface, and suggest that channel pores consisting of only the beta and gamma subunits can provide significant residual activity. This activity may be sufficient to explain the absence of a severe pulmonary phenotype in patients with PHA-I.

Prospective analysis of KRAS, BRAF, and PIK3CA mutations and EGFR copy number in patients (pts) with locally advanced rectal cancer: A translational substudy of a clinical trial (SAKK 41/07) evaluating the effect of neoadjuvant chemoradiation (CRT) with or without panitumumab

Background: Prognostic and predictive markers are of great importance for future study designs and essential for the interpretation of clinical trials incorporating an EGFR-inhibitor. The current study prospectively assessed and validated KRAS, BRAF and PIK3CA mutations in rectal cancer patients screened for the trial SAKK41/07 of concomitant preoperative radio-chemotherapy with or without panitumumab.Methods: Macrodissection was performed on pretreatment formalin fixed paraffin embedded biopsy tissue sections to arrive at a minimum of 50% of tumor cells. DNA was extracted with the Maxwell 16 FFPE Tissue LEV DNA purification kit. After PCR amplification, mutations were identified by pyrosequencing. We prospectively analysed pretreatment biopsy material from 149 rectal cancer pts biopsies for KRAS (exon 2 codon 12 [2-12] and 13 [2-13], exon 3 codon 59 [3-59]) and 61 [3-61], exon 4 codon 117 [4-117] and 146 [4-146]). Sixty-eight pts (KRASwt exon 2, 3 only) were further analysed for BRAF (exon 15 codon 600) and PIK3CA (exon 9 codon 542, 545 and 546, exon 20 codon 1043 [20-1043] and 1047 [20-1047]) mutations, and EGFR copy number by qPCR. For the calculation of the EGFR copy number, we used KRAS copy number as internal reference standard. The calculation was done on the basis of the two standard curves relative quantification method.Results: In 149 screened pts with rectal cancer, the prevalence of KRAS mutations was 36%. Among the 68 pts enrolled in SAKK 41/07 based on initially presumed KRASwt status (exon 2/codons 12+13), 18 pts (26%) had a total of 23 mutations in the RAS/PIK3CA-pathways upon validation analysis. Twelve pts had a KRAS mutation, 7 pts had a PIK3CA mutation, 3 pts had a NRAS mutation, 1 patient a BRAF mutation. Surprisingly, five of these pts had double- mutations, including 4 pts with KRAS plus PIK3CA mutations, and 1 pt with NRAS plus PIK3CA mutations. The median normalized EGFR copy number was 1. Neither mutations of KRAS, BRAF, and PIK3CA, nor EGFR copy number were statistically associated with the primary study endpoint pCR (pathological complete regression).Conclusions: The prevalence of KRAS mutations in rectal and in colon cancer appears to be similar. BRAF mutations are rare; PIK3CA mutations are more common (10%). EGFR copy number is not increased in rectal cancer. A considerable number or KRAS exon 2 wt tumors harbored KRAS exon 3+4 mutations. Further study is needed to determine if KRAS testing should include exons 2-4.

Ins1 (Cre) knock-in mice for beta cell-specific gene recombination.

AIMS/HYPOTHESIS: Pancreatic beta cells play a central role in the control of glucose homeostasis by secreting insulin to stimulate glucose uptake by peripheral tissues. Understanding the molecular mechanisms that control beta cell function and plasticity has critical implications for the pathophysiology and therapy of major forms of diabetes. Selective gene inactivation in pancreatic beta cells, using the Cre-lox system, is a powerful approach to assess the role of particular genes in beta cells and their impact on whole body glucose homeostasis. Several Cre recombinase (Cre) deleter mice have been established to allow inactivation of genes in beta cells, but many show non-specific recombination in other cell types, often in the brain. METHODS: We describe the generation of Ins1 (Cre) and Ins1 (CreERT2) mice in which the Cre or Cre-oestrogen receptor fusion protein (CreERT2) recombinases have been introduced at the initiation codon of the Ins1 gene. RESULTS: We show that Ins1 (Cre) mice induce efficient and selective recombination of floxed genes in beta cells from the time of birth, with no recombination in the central nervous system. These mice have normal body weight and glucose homeostasis. Furthermore, we show that tamoxifen treatment of adult Ins1 (CreERT2) mice crossed with Rosa26-tdTomato mice induces efficient recombination in beta cells. CONCLUSIONS/INTERPRETATION: These two strains of deleter mice are useful new resources to investigate the molecular physiology of pancreatic beta cells.