Characterization of mouse <Emphasis Type="Italic">Dactylaplasia</Emphasis> mutations: a model for human ectrodactyly SHFM3

SHFM3 is a limb malformation characterized by the absence of central digits. It has been shown that this condition is associated with tandem duplications of about 500 kb at 10q24. The Dactylaplasia mice display equivalent limb defects and the two corresponding alleles (Dac ^1j and Dac ^2j ) map in the region syntenic with the duplications in SHFM3. Dac ^1j was shown to be associated with an insertion of an unspecified ETn-like mouse endogenous transposon upstream of the Fbxw4 gene. Dac ^2j was also thought to be an insertion or a small inversion in intron 5 of Fbxw4, but the breakpoints and the exact molecular lesion have not yet been characterized. Here we report precise mapping and characterization of these alleles. We failed to identify any copy number differences within the SHFM3 orthologous genomic locus between Dac mutant and wild-type littermates, showing that the Dactylaplasia alleles are not associated with duplications of the region, in contrast with the described human SHFM3 cases. We further show that both Dac ^1j and Dac ^2j are caused by insertions of MusD retroelements that share 98% sequence identity. The differences between the nature of the human and mouse genomic abnormalities argue against models proposed so far that either envisioned SHFM3 as a local trisomy or Dac as a mutant allele of Fbxw4. Instead, both genetic conditions might lead to complex alterations of gene regulation mechanisms that would impair limb morphogenesis. Interestingly, the Dac ^2j mutation occurs within a highly conserved element that may represent a regulatory sequence for a neighboring gene. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A cytoplasmic cAMP-binding protein in Dictyostelium discoideum

A cytoplasmic cAMP-binding protein from Dictyostelium discoideum was purified about 1200-fold. The binding protein is relatively specific for cAMP, but also binds some other adenine derivatives; it has a molecular weight of approximately 185,000 and an apparent K_D of 1 μM cAMP. The highest level of cytoplasmic cAMP-binding activity is found in amoebae which have been starved for 0–2 hr. Amoebal extracts contain inhibitors of cAMP binding which are removed by chromatography through Sephacryl S200.     

Spatial behaviour of European minkMustela lutreola and polecatMustela putorius in southwestern France

The European minkMustela lutreola Linnaeus, 1761 and the European polecatMustela putorius Linnaeus, 1758 are sympatric in southwestern France. They are related species but the former is highly threatened whereas the latter maintains good populations. Nine European mink and 14 polecats were radiotracked in the Landes de Gascogne region to compare their space use and to identify appropriate conservation measures for the European mink. Resting animals were located once a day and active animals were tracked by continuous monitoring. European mink had linear home ranges whose sizes were larger than predicted by Johnson’s model (mean±SD=2971±1888 ha in males and 257±113 ha in females). They travelled long inter-day distances (1.4±1.9 km in males and 0.4±0.6 km in females). Polecats had home ranges of various shapes (linear, circular or combined) and their sizes were consistent with Johnson’s model (707±779 ha in males and 51±58 ha in females). They also had shorter inter-day distances than mink (0.7±0.9 km in males and 0.2±0.4 km in females). However male polecats had longer activity bouts than male mink. Thus European mink exhibit large movements between small and distant activity areas while polecats compensate for their smaller range by a higher activity in restricted areas. The behaviour of the European mink appears to be an adaptation to habitats scattered over linear ranges. This extensive use of space suggests that conservation of this endangered species cannot be achieved in the confinement of Europe’s natural reserves. Conservation plans should aim at maintaining high quality habitats along entire river networks and ensuring safe movements for the animals, preventing particularly the risk of collisions with vehicles.