High mutation rate in mammalian mitochondrial DNA generates a highly divergent pool of alleles even within species that have dispersed and expanded in size recently. Phylogenetic analysis of 277 human mitochondrial genomes revealed a significant (P , 0.01) excess of rRNA and nonsynonymous base substitutions among hotspots of recurrent mutation. Most hotspots involved transitions from guanine to adenine that, with thymine-to-cytosine transitions, illustrate the asymmetric bias in codon usage at synonymous sites on the heavy-strand DNA. The mitochondrion-encoded tRNA Thr varied significantly more than any other tRNA gene. Threonine and valine codons were involved in 259 of the 414 amino acid replacements observed. The ratio of nonsynonymous changes from and to threonine and valine differed significantly (P ¼ 0.003) between populations with neutral (22/58) and populations with significantly negative Tajima's D values (70/76), independent of their geographic location. In contrast to a recent suggestion that the excess of nonsilent mutations is characteristic of Arctic populations, implying their role in cold adaptation, we demonstrate that the surplus of nonsynonymous mutations is a general feature of the young branches of the phylogenetic tree, affecting also those that are found only in Africa. We introduce a new calibration method of the mutation rate of synonymous transitions to estimate the coalescent times of mtDNA haplogroups.

Some insight into human evolution has been gained from the sequencing of four Y chromosome genes. Primary genomic sequencing determined gene SMCY to be composed of 27 exons that comprise 4,620 bp of coding sequence. The unfinished sequencing of the 5 portion of gene UTY1 was completed by primer walking, and a total of 20 exons were found. By using denaturing HPLC, these two genes, as well as DBY and DFFRY, were screened for polymorphic sites in 53-72 representatives of the five continents. A total of 98 variants were found, yielding nucleotide diversity estimates of 2.45 ؋ 10 ؊5 , 5.07 ؋ 10 ؊5 , and 8.54 ؋ 10 ؊5 for the coding regions of SMCY, DFFRY, and UTY1, respectively, with no variant having been observed in DBY. In agreement with most autosomal genes, diversity estimates for the noncoding regions were about 2-to 3-fold higher and ranged from 9.16 ؋ 10 ؊5 to 14.2 ؋ 10 ؊5 for the four genes. Analysis of the frequencies of derived alleles for all four genes showed that they more closely fit the expectation of a Luria-Delbrü ck distribution than a distribution expected under a constant population size model, providing evidence for exponential population growth. Pairwise nucleotide mismatch distributions date the occurrence of population expansion to Ϸ28,000 years ago. This estimate is in accord with the spread of Aurignacian technology and the disappearance of the Neanderthals. The human Y chromosome consists of a nonrecombining region (NRY), which makes up 95% of its length, flanked by pseudoautosomal regions (1). Aside from the absence of recombination, NRY differs from all other nuclear human chromosomes by its presence in males only, its common ancestry and persistent meiotic relationship with the X chromosome, and the tendency of its genes to degenerate during evolution. Other than for its role in male sex determination, mediated by the SRY gene (2), the Y chromosome has been perceived as functionally desolate. Recently, 20 genes or gene families have been identified in the NRY (3). They fall into two classes. One class of nine genes is expressed in many organs and has X homologs that escape X inactivation. Among them are the single-copy genes DBY, DFFRY, and UTY, all of which have been mapped into the deletion interval 5C, and SMCY, located in the interval 5O (3). Most of the other NRY genes are highly duplicated, including the 11 NRY genes that are expressed specifically in testes. By deletion mapping, putative roles in sex determination, germ-cell tumorigenesis, determination of stature, and spermatogenesis have been established for most of the NRY genes (3). In particular, deletion of the AZFa region that contains DBY, DFFRY, and UTY has been shown to disrupt spermatogenesis, causing infertility in otherwise healthy men (4). SMCY, on the other hand, has been found to contain the human H-Y epitope, H-Y͞HLA-B7, which alone or in part accounts for the male-specific transplantation antigen (5). SMCY's 65% homology to the retinoblastoma 2 gene suggests that the gene may code for a transcription factor (5)....

We analysed breast tumors and breast cancer cell lines for the expression of b-parvin (ParvB), an adaptor protein that binds to the integrin-linked kinase (ILK). Quantitative RT-PCR indicated that ParvB mRNA was downregulated, by at least 60%, in four of nine breast tumors, relative to patient-matched normal mammary gland tissue. We also found that ParvB protein levels were reduced by X90% in five of seven advanced tumors, relative to matched normal breast tissue. Conversely, ILK protein and kinase activity levels were elevated in these tumors, suggesting that downregulation of ParvB stimulates ILK signaling. Western blot analyses indicated very low levels of ParvB protein in MDA-MB-231 and MCF7 breast cancer cells, facilitating functional studies of the effects of ParvB on ILK signaling. Expression of ParvB in MDA-MB-231 and MCF7 cells increased cell adhesion to collagen. ParvB inhibited ILK kinase activity, anchorageindependent cell growth and in vitro matrigel invasion by MDA-MB-231 cells. EGF-induced phosphorylation of two ILK targets, PKB (Ser473) and glycogen synthase kinase 3b (Ser9), was also inhibited by ParvB. These results indicated that ParvB inhibits ILK signaling downstream of receptor tyrosine kinases. Our results suggest that loss of ParvB expression is a novel mechanism for upregulating ILK activity in tumors.

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In our ex vivo model, externally irrigated radiofrequency catheters produced drag lesion volumes equal to or larger than those created by a point-by-point method.We also found decreased lesion size due to intermittent contact can be overcome by increasing duration of ablation time.