A transgene insertion at perinatal lethality (ple) is associated with abnormalities of the cortex

In an inbred genetic background, mice homozygous for a transgene insertion at perinatal lethality (ple) were found to be significantly smaller than their heterozygous or wild-type siblings at birth, and rarely survived for more than 48 h. Homozygous progeny of ple mice obtained from a cross with a different strain were viable, but were still not obtained in the expected numbers, demonstrating some deleterious affect of this mutation even in a hybrid genetic background. Homozygous mice demonstrate variable expression of abnormalities in brain development. These usually appear as focal cortical ectopias, but also include other abnormalities, such as polymicrogyria. The genomic sequences corresponding to the region disrupted by the transgene were cloned by isolating a junction fragment between transgenic and wild-type sequences, which was then used to obtain the corresponding region of wild-type genomic DNA. Since some probes from this region do not hybridize with genomic DNA from homozygous ple mice, it appears likely that a deletion event coincided with the transgene insertion.