Biomedical subjects

J M Pisenti

Publications and source records attributed to J M Pisenti.

3 recordsLinked to original sources

PubMed1996

The chick limbless mutation causes abnormalities in limb bud dorsal-ventral patterning: implications for the mechanism of apical ridge formation.

In chick embryos homozygous for the limbless mutation, limb bud outgrowth is initiated, but a morphologically distinct apical ridge does not develop and limbs do not form. Here we report the results of an analysis of gene expression in limbless mutant limb buds. Fgf4, Fgf8, Bmp2 and Msx2, genes that are expressed in the apical ridge of normal limb buds, are not expressed in the mutant limb bud ectoderm, providing molecular support for the hypothesis that limb development fails in the limbless embryo because of the inability of the ectoderm to form a functional ridge. Moreover, Fgf8 expression is not detected in the ectoderm of the prospective limb territory or the early limb bud of limbless embryos. Since the early stages of limb bud outgrowth occur normally in the mutant embryos, this indicates that FGF8 is not required to promote initial limb bud outgrowth. In the absence of FGF8, Shh is also not expressed in the mutant limb buds, although its expression can be induced by application of FGF8-soaked beads. These observations support the hypothesis that Fgf8 is required for the induction of Shh expression during normal limb development. Bmp2 expression was also not detected in mutant limb mesoderm, consistent with the hypothesis that SHH induces its expression. In contrast, SHH is not required for the induction of Hoxd11 or Hoxd13 expression, since expression of both these genes was detected in the mutant limb buds. Thus, some aspects of mesoderm A-P patterning can occur in the absence of SHH and factors normally expressed in the apical ridge. Intriguingly, mutant limbs rescued by local application of FGF displayed a dorsalized feather pattern. Furthermore, the expression of Wnt7a, Lmx1 and En1, genes involved in limb D-V patterning, was found to be abnormal in mutant limb buds. These data suggest that D-V patterning and apical ridge formation are linked, since they show that the limbless mutation affects both processes. We present a model that explains the potential link between D-V positional information and apical ridge formation, and discuss the possible function of the limbless gene in terms of this model.

Animals↗

PubMed1993

Making the connection: exploring classical concepts in normal and abnormal limb development using contemporary approaches.

Classical studies of the vertebrate limb have provided a firm foundation for recent investigations into the molecular control of mechanisms governing limb patterning. The early studies revealed the importance of inductive tissue interactions in developing systems, the spatiotemporal restrictions of these interactions, and the conservation of inductive signals between different tissues and even different species. They incorporated a number of different experimental approaches, including: homologous and heterologous tissue grafting and recombination, the investigation of several limb mutations, and examination of the response of normal limb tissue to a variety of teratogenic treatments. While some of the mutations studied only affected the limbs, most were highly pleiotropic, producing complex syndromes that altered the development of several embryonic structures in addition to the limbs. Some of these syndromes could be partially or completely phenocopied (mimicked) by specific chemical or physical treatments. One such gene-phenocopy pairing that we have studied is that of the mutation wingless-2 and the syndrome produced by treatment with retinoic acid. Another aspect of abnormal pattern formation we explored is the interaction between wingless-2 and eudiplopodia.

Animals↗

PubMed1983

Inbreeding effects on reproductive traits in the ring-necked pheasant.

Ten inbred lines of Ring-necked pheasants were established in 1978 and mated for four generations using a system of repeated backcrossing of daughters to a common sire. In the event the old sire died, the surviving daughters were mated to a surviving brother or half-brother of the same generation. Only 4 of 10 original inbred lines survived four generations of backcrossing; two involved matings with the original sire and two with brothers or half-brothers of Generations 1 and 3, respectively. Egg production, hatchability, and viability were the three traits most affected by inbreeding depression. For 4 generations of inbreeding, the coefficients of regression for all inbred lines on a 10% increase in inbreeding were -5.89, -.42, -1.73, and -3.04 for egg production, egg weight, fertility, and hatchability, respectively. Inbreeding had less severe effects on reproductive traits in two of the four surviving lines. There is evidence that intense early selection among lines for high performance after one generation of inbreeding F = .250 will enhance the success of establishing highly viable inbred lines of pheasants.

Animals↗