To explore the origins and consequences of tetraploidy in the African clawed frog, we sequenced the Xenopus laevis genome and compared it to the related diploid X. tropicalis genome. We demonstrate the allotetraploid origin of X. laevis by partitioning its genome into two homeologous subgenomes, marked by distinct families of “fossil” transposable elements. Based on the activity of these elements and the age of hundreds of unitary pseudogenes, we estimate that the two diploid progenitor species diverged ~34 million years ago (Mya) and combined to form an allotetraploid ~17–18 Mya. 56% of all genes are retained in two homeologous copies. Protein function, gene expression, and the amount of flanking conserved sequence all correlate with retention rates. The subgenomes have evolved asymmetrically, with one chromosome set more often preserving the ancestral state and the other experiencing more gene loss, deletion, rearrangement, and reduced gene expression.

No abstract

CD26, the T cell activation molecule dipeptidyl peptidase IV (DPPIV), associates with a 43-kilodalton protein. Amino acid sequence analysis and immunoprecipitation studies demonstrated that this 43-kilodalton protein was adenosine deaminase (ADA). ADA was coexpressed with CD26 on the Jurkat T cell lines, and an in vitro binding assay showed that the binding was through the extracellular domain of CD26. ADA deficiency causes severe combined immunodeficiency disease (SCID) in humans. Thus, ADA and CD26 (DPPIV) interact on the T cell surface, and this interaction may provide a clue to the pathophysiology of SCID caused by ADA deficiency.

The fifth component of the COP9 signalosome complex, Jab1/CSN5, directly binds to and induces specific downregulation of the cyclin-dependent kinase inhibitor p27 (p27 Kip1 ). Nuclear-cytoplasmic translocation plays an important role because leptomycin B (LMB), a chemical inhibitor of CRM1-dependent nuclear export, prevents p27 degradation mediated by Jab1/CSN5. Here we show that Jab1/CSN5 functions as an adaptor between p27 and CRM1 to induce nuclear export and subsequent degradation. Jab1/CSN5, but not p27, contains a typical leucinerich nuclear export signal (NES) sequence conserved among different species, through which CRM1 bound to Jab1/CSN5 in an LMB-sensitive manner. Alteration of conserved leucine residues to alanine within Jab1/CSN5-NES abolished the interaction with CRM1 in vitro and impaired LMB-sensitive nuclear export and the ability to induce p27 breakdown in cultured cells. A Jab1/CSN5 truncation mutant lacking NES reversed p27 down-regulation induced by the full-length Jab1/CSN5, indicating that this mutant functions as a dominant negative (DNJab1). Introduction of DN-Jab1 into proliferating fibroblasts increased the level of p27 protein, thereby inducing growth arrest of the cells. Random mutagenesis analysis revealed that specific aspartic acid, leucine, and asparagine residues contained in the Jab1/CSN5-binding domain of p27 were required for interaction with Jab1/CSN5 and for down-regulation of p27. Glycerol gradient and cell fractionation experiments showed that at least two different forms of Jab1/CSN5-containing complexes existed within the cell. One is the conventional 450-kDa COP9 signalosome (CSN) complex located in the nucleus, and the other is much smaller (around 100-kDa), containing only a subset of CSN components (CSN4 -8 but not CSN1-3), and mainly located in the cytoplasm. Treatment of cells with LMB greatly reduced the level of the smaller complex, suggesting that it originated from the CSN complex by nuclear export. Besides Jab1/CSN5, CSN3, ؊6, ؊7, and ؊8 were capable of inducing p27 down-regulation, when ectopically expressed. These results indicate that cytoplasmic shuttling regulated by Jab1/CSN5 and other CSN components may be a new pathway to control the intracellular abundance of the key cell cycle regulator.

No abstract

The replication of Nb 2 Node rat lymphoma cells in suspension culture is specifically stimulated by lactogenic hormones. Human (hPRL), ovine, bovine, and rat PRLs stimulated replication in a dose-dependent manner in the concentration range of 10 pg/ml to 1 ng/ml. Human, ovine, and bovine placental lactogens were similarly active. In addition, cell replication was stimulated by human GH (hGH), which is known to have lactogenic activity. Other hormones and growth factors examined were inactive. The growth stimulatory effects of hPRL and hGH were completely inhibited when excess anti-hPRL and anti-hGH, respectively, were added to the medium. A bioassay based on the response of the Nb 2 Node lymphoma cells to lactogenic hormones has been developed. Human serum stimulated cell replication. The effect was completely abolished if excess antibodies to both hPRL and hGH were present. The stimulation obtained with a number of human serum samples correlated very well with the sum of the hPRL and hGH concentrations in the sera, as determined by RIA (r = 0.95; P < 0.001). The concentrations of either hPRL or hGH in human serum could be individually determined by specifically blocking the growth stimulatory effect of the other hormone by adding excess anti-hGH or anti-hPRl. The sensitivity of this bioassay for PRL and hGH in serum exceeds that of RIAs.

We report on the clinical and molecular findings in 25 males and three females with Kallmann syndrome (KS) aged 10-53 yr. Ten males were from five families, and the remaining 15 males and three females were apparently sporadic cases. Molecular studies were performed for Kallmann syndrome 1 (KAL1) and fibroblast growth factor receptor 1 (FGFR1, also known as KAL2) by sequence analysis for all the coding exons, by PCR-based deletion analysis, and by fluorescence in situ hybridization (FISH) analysis, showing six novel and two recurrent intragenic KAL1 mutations in seven familial and four sporadic male cases and two novel intragenic FGFR1 mutations in two sporadic male cases. In addition, submicroscopic deletions at Xp22.3 involving VCX-A, STS, KAL1, and OA1 were identified in three familial cases and one sporadic male case affected by a contiguous gene syndrome. Clinical assessment in the 15 males with KAL1 mutations showed normal and borderline olfactory function in two males and right-side dominant renal lesion in seven males, in addition to variable degrees of hypogonadotropic hypogonadism (HH) in all the 15 males and olfactory dysfunction in 13 males. The two males with FGFR1 mutations had HH and anosmia and lacked other features. Clinical features in the remaining 11 cases with no demonstrable KAL1 or FGFR1 mutations included right renal aplasia in one female, cleft palate in one male, cleft palate and perceptive deafness in one male, and dental agenesis and perceptive deafness in one male, in addition to a variable extent of HH and olfactory dysfunction. The results suggest the following: 1) KAL1 mutations might be more prevalent in the Japanese patients than previously estimated in the Caucasian patients and can be associated with apparently normal olfactory function; 2) FGFR1 mutations account for approximately 10% of KS patients, as previously reported in the Caucasian patients, and can result in HH and olfactory dysfunction-only phenotype; and 3) renal aplasia, which is characteristic of KAL1 mutations, and cleft palate and dental agenesis, which are characteristic of FGFR1 mutations, can occur in patients without KAL1 and FGFR1 mutations.

Inactivating mutations in the 25-hydroxyvitamin D3 1alpha-hydroxylase gene are a cause of pseudovitamin D-deficiency rickets.