Sense and antisense transcripts of the apolipoprotein E gene in normal and ApoE knockout mice, their expression after spinal cord injury and corresponding human transcripts.

The apolipoprotein E (ApoE) gene has been linked to maladies such as hypercholesterolemia, CNS injury and disease. In this study, we present evidence that, in addition to the known transcript (ApoE S1) that translates into ApoE, there are three additional transcripts in mice. Two of these transcripts, ApoE S2 and ApoE S3, which are predicted to be transmembrane proteins, are transcribed from the sense strand. ApoE AS1 is transcribed from the antisense strand and is complementary to exon 4 of ApoE S1. The open reading frame of ApoE AS1 is conserved between human and mouse. The antisense transcript falls within the region of the human epsilon 4 allele that has been linked to the familial onset form of Alzheimer's disease. We also demonstrate the expression of ApoE S3 and ApoE AS1 in ApoE knockout mice, and ApoE S1 and ApoE S2 do not get transcribed. We had previously identified ApoE S1 as being upregulated in mice after spinal cord injury. In this study, we show that in spinal cord-injured C57BL/6 mice, both ApoE S1 and ApoE S3 transcripts are 10-fold upregulated and the antisense ApoE AS1 is 100-fold upregulated compared with normal levels. Such data suggest that these alternate transcripts are involved in the molecular pathogenesis of CNS disease and perhaps in ApoE expression in general, as we show that ApoE S2 and AS1 are also transcribed in human.

Matrix metalloproteinase activity correlates with blastema formation in the regenerating MRL mouse ear hole model.

The MRL mouse was proposed as a model of mammalian regeneration because it can close ear holes completely with the restoration of normal tissue. This regeneration process involves the formation of a blastema during healing, the re-appearance of cartilage and hair follicles, and healing without scarring. Such a process requires extensive tissue remodeling. To characterize differences in ear wounding responses between regenerating and nonregenerating mice, we examined and compared the extracellular matrix remodeling and the matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) response in the MRL and C57BL/6 mouse strains after injury. We found a correlation between the MRL's ability to break down the basement membrane, form a blastema, and close ear hole wounds and an inflammatory response with neutrophils and macrophages seen in the ear after injury. These cells were positive for MMP-2 and MMP-9 as well as TIMP-2 and TIMP-3. Clear differences between the MRL and B6 response to injury were seen that could explain the differences in healing and blastema formation in the MRL and lack of it in the B6 mice. This finding was further supported by enzyme activity as determined by gelatin zymography.

Expression of preadipocyte factor-1(Pref-1), a delta-like protein, in healing mouse ears.

Preadipocyte factor-1 (Pref-1), a delta-like protein containing epidermal growth factor-repeats, is expressed in proliferating cells in a variety of tissues and is believed to be involved in maintaining the undifferentiated state of these cells. Using microarray analysis, reverse transcriptase-polymerase chain reaction, in-situ hybridization, and immunohistochemistry, we have identified Pref-1 expression in the healing ears of two strains of mice, MRL and C57BL/6. MRL is unusual in that ear punches completely regenerate the ear tissue along with new cartilage with no scarring. Pref-1 is more highly expressed in the MRL wounds, is uniquely found in a condensation of cells within the regenerating tissue of the blastema, and may contribute to the regenerative capacity of the MRL ear wound.