Evolution

Chemical etiology of nucleic acid structure: The α-threofuranosyl-(3′–>2′) oligonucleotide system. Schöning, K. -U. et al. Science 290 , 1347–1351 (2000) [PubMed]

Schöning et al. have synthesized and studied a chemical analogue of RNA, which is derived from a sugar ring that contains four carbons (tetrose) instead of the more usual five found in ribose. This simple RNA, called L-α-threofuranosyl or TNA, can form stable double helices with itself and also with complementary RNAs and DNAs. The cross-pairing properties and the simplicity of its self-assembly make TNA a good candidate for a natural nucleic acid and a possible precursor of RNA.

Developmental biology

Genetic control and evolution of sexually dimorphic characters in Drosophila. Kopp, A. et al. Nature 408 , 553–559 (2000) [PubMed]

Abdominal pigmentation and morphology in Drosophila melanogaster are sexually dimorphic features that require the homeotic and the sex-determination pathways. This paper reveals the genetic circuitry that integrates the two signalling inputs and that culminates in the differential expression of bric-a-brac (bab) in the two sexes. Expression studies in monomorphic species indicate that changes in the way that sex- and homeotic-specific pathways control bab expression might have been responsible for the evolution of some sexually dimorphic characters.

Human genetics

Dominant modifier DFNM1 suppresses recessive deafness DFNB26 . Riazuddin, S. et al. Nature Genet. 26 , 431–434 (2000) [PubMed]

While mapping a new, recessive deafness locus (DFNB26) in a large consanguineous family, these authors discovered a dominant, deafness-suppressing modifier locus. When family members were typed for the DFNB26-linked haplotype on chromosome 4q31, homozygotes were found among both deaf and hearing family members. A second genome scan to test for modifier loci revealed a dominant modifier, DFNM1, on chromosome 1. Candidate genes at both loci are being investigated.

RNA editing

Requirement of the RNA editing deaminase ADAR1 gene for embryonic erythropoiesis. Wang, Q. et al. Science 290 , 1765–1768 (2000) [PubMed]

Just how important is RNA editing? Wang et al. answered this question by making a knockout of Adar1, which encodes a member of the Adar family of RNA editors. When the authors created mouse chimeras derived from Adar −/+ ES cells, they found high levels of embryonic lethality. Embryos died at a critical stage in erythropoiesis. The results suggest that some processes in embryogenesis are very sensitive to levels of RNA editing. .