A THEMIS:SHP1 complex promotes T‐cell survival

THEMIS is critical for conventional T‐cell development, but its precise molecular function remains elusive. Here, we show that THEMIS constitutively associates with the phosphatases SHP1 and SHP2. This complex requires the adapter GRB2, which bridges SHP to THEMIS in a Tyr‐phosphorylation‐independent fashion. Rather, SHP1 and THEMIS engage with the N‐SH3 and C‐SH3 domains of GRB2, respectively, a configuration that allows GRB2‐SH2 to recruit the complex onto LAT. Consistent with THEMIS‐mediated recruitment of SHP to the TCR signalosome, THEMIS knock‐down increased TCR‐induced CD3‐ζ phosphorylation, Erk activation and CD69 expression, but not LCK phosphorylation. This generalized TCR signalling increase led to augmented apoptosis, a phenotype mirrored by SHP1 knock‐down. Remarkably, a KI mutation of LCK Ser59, previously suggested to be key in ERK‐mediated resistance towards SHP1 negative feedback, did not affect TCR signalling nor ligand discrimination in vivo. Thus, the THEMIS:SHP complex dampens early TCR signalling by a previously unknown molecular mechanism that favours T‐cell survival. We discuss possible implications of this mechanism in modulating TCR output signals towards conventional T‐cell development and differentiation.     

Reproductive Biology ofDalbergia miscolobiumBenth. (Leguminosae-Papilionoideae) in SE Brazil: The Effects of Pistillate Sorting on Fruit-set

The breeding system ofDalbergia miscolobiumBenth. was investigatedby means of controlled pollinations and studies of post-pollinationevents in pistils. This species does not have homomorphic self-incompatibility,but crossed flowers always have higher fruit set than selfs,despite the fact that embryo development may be initiated inselfed pistils. It is suggested that deleterious recessive alleles,which lead to abortion of most selfed seeds, together with somematernal resource limitation, result in low fruiting success.Copyright1998 Annals of Botany Company Dalbergia miscolobiumBenth., Leguminosae, breeding system, pistillate sorting, fruiting success, seed set.     

PHENOTYPIC CHANGES IN THE PROGENY OF NUCELLA LAPILLUS (GASTROPODA) TRANSPLANTED FROM AN EXPOSED SHORE TO SHELTERED INLETS

Nucella lapillus adults were transplanted from the exposed northCornish coast (Bude) to two sheltered inlets in south Devon(Dart Estuary and Plymouth Sound), sites where the native populationshad ceased breeding as a result of sterilisation by tributyltin(TBT) pollution. The transplants produced progeny, many of whichsurvived to maturity and beyond (6 + years). The shell formof Bude individuals is typical of animals exposed to severewave-action, i.e. of light construction with a large apertureto accommodate a broad foot allowing for strong adhesion. However,in contrast, the shell form of the progeny differed markedlyfrom that of their parents; they had the characters associatedwith development under sheltered conditions and subject to severecrab predation, i.e. a robust structure and small aperture.Statistical analysis of the shell characters of the two generationsindicated highly significant differences. It is concluded theseobservations provide evidence of the remarkable plasticity inthe shell form of N lapillus in that both ‘exposed morph’and ‘sheltered morph’ can be produced by the samegene pool when subject to the actions of the appropriate selectionpressures. (Received 25 September 1992; accepted 14 October 1992)     

Species-wide distribution of highly polymorphic minisatellite markers suggests past and present genetic exchanges among house mouse subspecies

Background  

Four hypervariable minisatellite loci were scored on a panel of 116 individuals of various geographical origins representing a large part of the diversity present in house mouse subspecies. Internal structures of alleles were determined by minisatellite variant repeat mapping PCR to produce maps of intermingled patterns of variant repeats along the repeat array. To reconstruct the genealogy of these arrays of variable length, the specifically designed software MS_Align was used to estimate molecular divergences, graphically represented as neighbor-joining trees.