'Crommelin-type' symmetrical tetramelic reduction deformity: a new case and breakpoint mapping of a reported case with de-novo t(2;12)(p25.1;q23.3).

We report a male fetus with symmetrical peromelic reduction of the upper limbs (missing distal, mesial and proximal elements) and symmetrical phocomelic reduction of the lower limbs (missing proximal and mesial elements) without other major malformations. We identified 11 previously reported cases with very similar features and have named this entity 'Crommelin-type' symmetrical tetramelic reduction deformity. Interphase fluorescence in-situ hybridization on isolated nuclei from paraffin-embedded tissue was used to map the breakpoints in a previously reported case with a de-novo t(2;12)(p25.1;q23.3). The 2p25.1 breakpoint disrupted ROCK2, encoding Rho-associated, coiled-coil-containing protein kinase. The 12q23.3 breakpoint maps 0-25 kb 5 of CMKLR1, encoding chemokine-like receptor 1. Homozygous loss-of-function of either gene causes no major limb effect in mouse embryos. However, Cmklr1 shows both site-specific and stage-specific expression in mouse limb buds, but no mutations were identified in CMKLR1 or a nearby putative cis-regulatory region in the new case. We cannot assign a specific genetic mechanism in the translocation case but developmental disregulation of gene expression at one, or both, breakpoints may provide an explanation for the phenotype.

Using BAC clones to characterize unbalanced chromosome abnormalities in interphase cells.

Carriers of balanced translocations usually carry alterations in gene sequences, which lead to dysfunction during early and late embryogenesis. Related spatial rearrangement causes either cumulative delay in cell cycles and/or anomalies in transcription and translation. This has also an important impact at the time of genomic activation, the longest cell cycle of preimplantation development. Carrier patients may be affected either with primary infertility or by repeated miscarriages [Hum. Reprod. 12 (1997) 2019.]. Assuming that a fraction of the germ cells is karyotypically normal, these patients would greatly benefit from efficient procedures for generation and use of breakpoint-specific DNA hybridisation probes in preconception and preimplantation genetic diagnosis (PGD) after polar body or blastomere biopsy of the embryos. The objective of this research was to design an approach of patient-specific probes for preimplantation diagnosis of chromosome translocations and which could be used eventually to select chromosomally normal embryos from balanced or unbalanced interphase cells prior to their transfer to the mother's womb. This approach was used for a couple, where the female partner was a carrier of a balanced translocation 46,XX,t(4;12)(p16.1;q24.31). First, BAC/PAC clones were chosen from specific chromosome bands from the genome sequence that hybridise adjacent to the chromosomal breakpoints or span them. Then, the probes and hybridisation conditions were optimised using unrelated normal amniocytes, lymphoblastoid cells and lymphocytes from the carrier to increase hybridisation signal intensity and decrease background. Finally, the probes were tested on target cells before they were used for mimicking preconception or preimplantation genetic diagnosis. Three slides were analysed blindly from a normal karyotype, an unbalanced and a balanced translocation. A total of 78 cells were analysed of which in the slide A 19/22 (86%) were found to be unbalanced, in slide B 25/31 (81%) were normal and in slide C 21/25 (84%) were balanced. Thus, it was demonstrated that cells with known structural abnormalities could be detected, based on hybridisation of breakpoint spanning bacterial artificial chromosome (BAC) DNA probes in interphase cells.

The LEF1/beta -catenin complex activates movo1, a mouse homolog of Drosophila ovo required for epidermal appendage differentiation.

Drosophila ovo/svb (dovo) is required for epidermal cuticle/denticle differentiation and is genetically downstream of the wg signaling pathway. Similarly, a mouse homolog of dovo, movo1, is required for the proper formation of hair, a mammalian epidermal appendage. Here, we provide biochemical evidence that movo1 encodes a nuclear DNA binding protein (mOvo1a) that binds to DNA sequences similar to those that dOvo binds to, further supporting the notion that mOvo1a and dOvo are genetically and biochemically homologous proteins. Additionally, we show that the movo1 promoter is activated by the lymphoid enhancer factor 1 (LEF1)/beta-catenin complex, a transducer of wnt signaling. Collectively, our findings suggest that movo1 is a developmental target of wnt signaling during hair morphogenesis in mice, and that the wg/wnt-ovo link in epidermal appendage regulatory pathways has been conserved between mice and flies.