Developmental Biology

Conserved role of nanos proteins in germ cell development. Tsuda, M. et al. Science 301, 1239–1241 (2003)

In Drosophila, nanos encodes an RNA-binding protein that is required maternally for the migration of the primordial germ cells into the gonad. Now, two mouse nanos homologues, nanos2 and nanos3, have been cloned. The knockout phenotypes of these two genes — lack of male germ cells in nanos2−/− mice and lack of germ cells in both sexes in nanos3−/− animals — indicate that despite apparent differences, the mechanism of germ-cell specification is conserved between vertebrates and invertebrates.

Developmental Biology

GATA-3: an unexpected regulator of cell lineage determination in skin. Kaufman, C. K. et al. Genes Dev. 17, 2108–2122 (2003)

The GATA-3 transcription factor is known to be required in lymphocyte differentiation. A microarray screen showed that GATA-3 is also expressed in the inner root sheath (IRS) cells — those that guide the developing hair shaft to the skin surface — early during hair morphogenesis. This evidence, together with the absence of the IRS in GATA-3-null mice and the aberrant structure of the mutant hair, points to a new function for GATA-3 in the differentiation of epidermal stem cells.

Evolution

Parasite selection for immunogenetic optimality. Wegner, K. M. et al. Science 301, 1343 (2003)

Theoretical models predict that the highly polymorphic genes of the vertebrate major histocompatibility (MHC) complex, which help to fight parasite infection, should exist at an intermediate level of diversity: too little diversity would impair pathogen recognition whereas too much would increase the likelihood of reacting against self-peptides. Wegner and colleagues have now tested the theory by infecting stickleback fish of varying levels of MHC diversity with several parasites. As predicted, fish with intermediate MHC diversity levels had the lowest infection rate.

Functional Genomics

The human transcriptome map reveals extremes in gene density, intron length, GC content, and repeat pattern for domains of highly and weakly expressed genes. Versteeg, R. et al. Genome Res. 13, 1998–2004 (2003)

The authors construct a new human transcriptome map to physically characterize clusters of highly expressed genes. They find that they are GC rich and contain many SINE but few LINE repeats. Genes that lie within these so-called ridges have shorter introns than genes that lie elsewhere. They also find evidence of clusters of weakly expressed genes, which they call antiridges.