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The emergence of genetic diseases and evolutionary processes are associated with the flow of genetic information from one generation to another, in which genetic information carried by gametes can be changed by the appearance of de novo germline mutations. The rate of germline mutations determines the rate of evolution and the incidence of heritable disorders. Despite the great theoretical and practical importance, the problem of establishing mutation rates and their dependence on different factors remains scarcely studied, and the mutation rate values obtained by different methods vary considerably. The review discusses different ways of estimating the rate of these mutations and makes an attempt to explain the reasons for discrepancies in the data obtained. Three levels of the mutation formation are considered: (1) mutations that are formed during the development of a given individual during gametogenesis (basic mutations); (2) mutations transmitted to offspring and determining differences in the genomes of consecutive generations (parents and offspring), which include basic mutations and possible changes resulting from complex processes of sperm transfer to oocyte, fertilization, and subsequent events that lead to only one viable offspring of hundreds of millions spermatozoa and oocytes; (3) mutations which are formed at level 2, fixed in evolution, and determine evolutionary processes and differences between genomes, in particular, of hominoids, hominids, and hominins.

SUMMARY Here we directly compared gene expression profiles in human esophageal squamous cell carcinomas and in human fetal esophagus development. We used the suppression subtractive hybridization technique to subtract cDNAs prepared from tumor and normal human esophageal samples. cDNA sequencing and reverse transcription polymerase chain reaction (RT-PCR) analysis of RNAs from human tumor and the normal esophagus revealed 10 differentially transcribed genes: CSTA, CRNN, CEACAM1, MAL, EMP1, ECRG2, and SPRR downregulated, and PLAUR, SFRP4, and secreted protein that is acidic and rich in cysteine upregulated in tumor tissue as compared with surrounding normal tissue. In turn, genes up- and downregulated in tumor tissue were down- and upregulated, respectively, during development from the fetal to adult esophagus. Thus, we demonstrated that, as reported for other tumors, gene transcriptional activation and/or suppression events in esophageal tumor progression were opposite to those observed during development from the fetal to adult esophagus. This tumor ‘embryonization’ supports the idea that stem or progenitor cells are implicated in esophageal cancer emergence.

Head-to-head genes with a short distance between their transcription start sites may constitute up to 10% of all genes in the genomes of various species. It was hypothesized that this intergenic space may represent bidirectional promoters which are able to initiate transcription of both genes, but the true bidirectionality was proved only for a few of them. We present experimental evidence that, according to several criteria, a 269 bp region located between the PSENEN and U2AF1L4 human genes is a genuine bidirectional promoter regulating a concerted divergent transcription of these genes. Concerted transcription of PSENEN and U2AF1L4 can be necessary for regulation of T-cell activity.