Comparative Expression Studies Research Articles

The molecular basis of a familial apoE deficiency. An acceptor splice site mutation in the third intron of the deficient apoE gene.

The molecular basis of the familial apoE deficiency was investigated by gene cloning and comparative expression studies of the normal and the deficient apoE gene. For the latter studies the apoE genes were placed under the control of the mouse metallothionein I promoter in a bovine papilloma virus vector. The studies showed that in the normal gene the mouse metallothionein I promoter directs the synthesis of normal apoE mRNA and protein. In contrast, in the deficient apoE gene the same promoter directs the synthesis of two abnormal apoE mRNA forms, which are similar to those observed in the peripheral blood monocyte macrophage cultures of the patient. Restriction analysis of the cloned gene and partial DNA sequence has shown an A to G substitution in the penultimate 3' nucleotide of the third intron of the apoE gene. This single base substitution abolishes the correct 3' splice site thus creating two abnormally spliced mRNA forms. The smaller form contains 53 nucleotides and the larger form contains the entire third intron of the apoE gene. Both of these mRNA species contain chain termination codons within the intronic sequence and code for short apoE peptides that are not detectable by gel electrophoretic techniques. These findings show that this form of familial apoE deficiency results from a point mutation in the 3' splice junction of the third intron of the apoE gene. Furthermore, the expression system we have employed to study apoE deficiency can be utilized to analyze a broad spectrum of genetic diseases associated with mRNA processing mutations.

Patterns of expression of class I antigens in the tissues of congenic strains of rat.

A comparative study of expression of class I major histocompatibility (MHC) antigens among lung, spleen, kidney, heart, liver, and brain tissues of the rat was performed. Monoclonal antibodies (MAbs) against RT1Aa determinants were conjugated to 125I and applied to frozen sections. Resulting autoradiograms showed antigen reactivity in lymphoid tissue, bronchial and alveolar epithelium, and endothelium of the lung. The lymphoid tissue of the lung and spleen demonstrated the antigen after shorter autoradiographic exposures than was required for the epithelial components of these organs. The kidneys were heavily labeled over the glomeruli, but less intensely over the tubular epithelium. RT1A antigen content of capillary endothelium of the heart was demonstrable before that of the muscle bundles. In the liver, autoradiographic sections revealed high determinant density in sinusoidal regions. Brain sections show reproducibly low levels of labeling, with the exception of vascular structures. All of these tissues from PVG-RT1c and PVG-RT1u animals show only background labeling.

Comparative Study of Phenotypic Expression of Mice Trisomy 16 by Different Female Strains: Attempt at an Animal Model for Human Trisomy 21

ABSTRACT Mouse trisomy 16, which was induced by mating males of Rb(16.17)7 Bnr/Rb(9.16)9Rma with three different strains of female, C57BL/6, C57BL/10 and C3H/He, was examined in fetuses and newborns in terms of incidence of occurrence, malformations and sex ratio. The incidence of trisomies tended to be higher in C3H/He than in C57BL/6 and C57BL/10. Trisomies could not survive beyond term in C57BL/6, which was most thoroughly examined in the three strains. Trisomy‐associated generalized edema, beginning to appear on day 14 of pregnancy on fetus's back, reached the maximum on day 16 in all strains. On cardiovascular anomalies, persistent common atrioventricular canal was observed in virtually all trisomies from C57BL/10 and C57BL/6, while in about 80% from C3H/He. In conotruncal region, all trisomies from former two crossing exhibited double outlet right ventricle or persistent truncus arteriosus. In addition to these anomalies, riding aorta was found in C3H/He. Hydroureter and hydronephrosis developed from day 17 of pregnancy in trisomies other than those in C57BL/10. The histological study of gonads revealed that trisomy 16 tended to be predominant in males of each crossing. The anomalies encountered in mouse trisomy 16, such as edema, persistent common atrioventricular canal, and hydroureter and hydronephrosis appeared to be in common with human trisomy 21 embryos and fetuses. The tendency of predominance of mouse trisomies in males may provide further homology to human trisomy 21. It is supposed that genetic background by different female strains may affect phenotypic expression of malformations. The extremely high incidence of cardiovascular anomalies is regarded as suitable material for elucidation of pathogenesis.