Genetic influence on neurogenesis in the dentate gyrus of adult mice

To address genetic influences on hippocampal neurogenesis in adult mice, we compared C57BL/6, BALB/c, CD1(ICR), and 129Sv/J mice to examine proliferation, survival, and differentiation of newborn cells in the dentate gyrus. Proliferation was highest in C57BL/6; the survival rate of newborn cells was highest in CD1. In all strains ≈60% of surviving newborn cells had a neuronal phenotype, but 129/SvJ produced more astrocytes. Over 6 days C57BL/6 produced 0.36% of their total granule cell number of 239,000 as new neurons, BALB/c 0.30% of 242,000, CD1 (ICR) 0.32% of 351,000, and 129/SvJ 0.16% of 280,000. These results show that different aspects of adult hippocampal neurogenesis are differentially influenced by the genetic background.

Permanence or change? The meaning of genetic variation

Selected aspects of the evolutionary process and more specifically of the genetic variation are considered, with an emphasis in studies performed by my group. One key aspect of evolution seems to be the concomitant occurrence of dichotomic, contradictory (dialect) processes. Genetic variation is structured, and the dynamics of change at one level is not necessarily paralleled by that in another. The pathogenesis-related protein superfamily can be cited as an example in which permanence (the maintenance of certain key genetic features) coexists with change (modifications that led to different functions in different classes of organisms). Relationships between structure and function are exemplified by studies with hemoglobin Porto Alegre. The genetic structure of tribal populations may differ in important aspects from that of industrialized societies. Evolutionary histories also may differ when considered through the investigation of patrilineal or matrilineal lineages. Global evaluations taking into consideration all of these aspects are needed if we really want to understand the meaning of genetic variation.

Computer-modeling origin of a simple genetic apparatus

This computer simulation is based on a model of the origin of life proposed by H. Kuhn and J. Waser, where the evolution of short molecular strands is assumed to take place in a distinct spatiotemporal structured environment. In their model, the prebiotic situation is strongly simplified to grasp essential features of the evolution of the genetic apparatus without attempts to trace the historic path. With the tool of computer implementation confining to principle aspects and focused on critical features of the model, a deeper understanding of the model's premises is achieved. Each generation consists of three steps: (i) construction of devices (entities exposed to selection) presently available; (ii) selection; and (iii) multiplication of the isolated strands (R oligomers) by complementary copying with occasional variation by copying mismatch. In the beginning, the devices are single strands with random sequences; later, increasingly complex aggregates of strands form devices such as a hairpin-assembler device which develop in favorable cases. A monomers interlink by binding to the hairpin-assembler device, and a translation machinery, called the hairpin-assembler-enzyme device, emerges, which translates the sequence of R1 and R2 monomers in the assembler strand to the sequence of A1 and A2 monomers in the A oligomer, working as an enzyme.