Genetical and embryological comparison of two mutations which cause foetal blebs in mice

Tissue morphogenesis and vascular stability require the Frem2 protein, product of the mouse myelencephalic blebs gene

Adhesive properties of cells undergoing morphogenetic rearrangements can be regulated either at the cellular level or by altering the environment in which rearrangements occur. Here, we describe the identification of a mutation (my(F11)) in the mouse extracellular matrix component Frem2, and provide evidence that suggests Frem2 expression creates an environment conducive to morphogenetic events. Loss of Frem2 function results in defects in developmental events associated with morphogenetic rearrangements of the vasculature and of tissues arising from all germ layers. The Frem2 transcript is restricted both spatially and temporally and appears in advance of cell rearrangement events. Thus, expression of Frem2 may dynamically alter the extracellular matrix to provide a substrate for cell migration and rearrangements during embryogenesis.

Immunohistochemical localization of Pax2 and associated proteins in the developing kidney of mice with renal hypoplasia

Pax2 has been identified as a key regulatory protein associated with renal developmental malformations. The purpose of this study was to determine whether Pax2 protein expression, and that of other proteins important for normal renal development, is abnormally distributed in the prenatal kidney of the Brachyrrhine (Br) mouse that displays heritable renal hypoplasia. Embryonic 3H1 +/+ and Br/Br mice were collected between E11.0 and E18.0. Routine light microscopy and immunohistochemical analysis using antibodies to Pax2, E-cadherin, fibronectin, laminin, and Type IV collagen were applied to sequential tissue sections. E-cadherin stained consistently in the renal tubules of both normal and mutant animals. Whereas the initial expression of Pax2 corresponded between normal and mutant kidneys, it became progressively limited to the nephrogenic zone in +/+ animals, while distributing erratically in the Br/Br kidney. Fibronectin was not expressed in the normal nephrogenic zone but remained abundantly distributed throughout the Br/Br kidney. Luminin and Type IV collagen staining revealed a deficiency in renal vasculature formation in Br/Br kidneys. Results suggest that initial morphological differentiation occurs normally in the Br kidney but that subsequent nephric formation is associated with abnormal distribution of Pax2 and ECM proteins. (J Histochem Cytochem 49:1081-1097, 2001)

External craniofacial features, body size, and renal morphology in prenatal brachyrrhine mice

The Brachyrrhine (Br) semidominant mouse mutant provides a useful model for studying factors responsible for midfacial hypoplasia. In order to determine early morphogenetic events responsible for midfacial hypoplasia in these mice, prenatal mutants must be differentiated from nonaffected littermates. The purpose of this study was to determine whether prenatal offspring from Br matings could be separated morphologically into groups of normal or midfacially deficient embryos. Thirty embryos resulting from Br matings were collected between day 15 and birth (Theiler stages 23-27). Qualitative observations on craniofacial morphology as well as renal morphology and histology suggested that embryos segregated into two distinct groups. External craniofacial and body measurements, collected from the embryos, as well as renal volumes, determined from computerized reconstructions of the kidneys, were subjected to quantitative analyses. A discriminant function analysis segregated the sample into two groups based primarily on midfacial length and renal volume. Bivariate regression analysis showed that midfacial length and renal volume differed significantly, and cranial length marginally so, between the two groups. The results indicate that a proportion of prenatal offspring from Br matings exhibits midfacial and renal hypoplasia and that these animals segregate completely from nonaffected embryos.

Congenital malformations in rats with the semilethal mutation fused pulmonary lobes

It has been demonstrated that an autosomal recessive gene, fused pulmonary lobes (fpl), causes fusion of the right pulmonary lobes with several associated malformations and a high incidence of death in homozygous newborns (Aoyama et al. Teratology 1988; 37:159-166). The aim of the present study was to investigate whether the deaths of fpl/fpl newborns were caused by functional abnormalities of the malformed lung or other associated malformations. Day-20 fpl/fpl and fpl/+ fetuses were weighed and examined for gross abnormalities. The lungs of selected fetuses were further examined for histological abnormalities. A wide variety of associated external, visceral, and skeletal anomalies as well as relatively lower body weights than those of phenotypically normal fpl/+ littermates were observed in the fpl/fpl fetuses. The associated anomalies consisted of hematomas and/or subcutaneous hemorrhages in the head, truncus and limbs, eyelid anomalies, CNS defects, lobation anomalies of the liver, hypoplasia of the spleen, partial absence of the skull bones, and dorsi- or ventriflexion of the phalanges of the limbs. Among them, CNS defects and partial absence of the skull bones were considered to be possible causes of newborn deaths. However, the incidence of these malformations was approximately 10% and was lower than the neonatal mortality, which had been estimated to be approximately 50% in the previous study (Aoyama et al. Teratology 1988; 37:159-166). The lungs of fpl/fpl fetuses consistently had hypoplasia of the intermediate lobe and fusion of the right pulmonary lobes. No histological changes suggesting postnatal respiratory insufficiency were found in the lungs of day-20 fpl/fpl fetuses, and the cause of newborn death remains unclear.

Lymphedema in Noonan syndrome: clues to pathogenesis and prenatal diagnosis and review of the literature

The Noonan syndrome (NS) is a true multiple congenital anomalies (MCA) syndrome with numerous manifestations. An association with lymphedema has been noted, but its pathogenesis is not fully understood. Nine new cases and a review of the literature explore the role of lymphedema in NS, including its pathogenesis, presentations, and phenotypic effects. Consideration is given to developmental stage at time of onset, chronicity, resolution, and anatomic site. It appears likely that lymphedema is a much more frequent concomitant in NS than previously realized. The major source of lymphedema in NS appears to be a presently undefined dysplasia of lymphatic vessels of unknown cause. Further study of lymphedema may provide an understanding of its role in shaping the NS phenotype. Comparison with other MCA syndromes and animal models is made in this regard. Relevance to prenatal diagnosis and treatment is discussed.