RESUMO
The Contactin-1 axonal glycoprotein (formerly F3/Contactin) plays a relevant role in cerebellar ontogenesis, as shown in Contactin-1 KO-mice and in transgenic mice misexpressing the corresponding cDNA from a heterologous promoter. Likewise, null mutant mice for the Collier/Olf1/Early B-cell family transcription factor EBF2, in which Purkinje neuron development is primarily affected, exhibit abnormalities in cerebellar corticogenesis. Here, to evaluate the contribution to the Ebf2 null phenotype of changes in the profile of Contactin-1, we study its expression in Ebf2 null mice. In addition, we explore the activation profile of the Cntn1 gene promoter upon transferring the Ebf2 mutation to transgenic mice expressing an enhanced green fluorescent protein reporter under control of Cntn1 gene regulatory sequences. In Ebf2 null mice, Contactin-1 protein expression and Cntn1 gene promoter activity are both downregulated during embryonic and early postnatal cerebellar development, both in the rostral and caudal folia, while in the latter an upregulation is observed at postnatal day 8. In vitro, vectors driving EBF1,2,3 transcription factors from a cytomegalovirus (CMV) promoter transactivate a Cntn1-Choline acetyltransferse (CAT) promoter-reporter construct in cotransfection assays and, accordingly, by chromatin immunoprecipitation, we show that the Cntn1 gene 5' flanking region is bound by the EBF2 transcription factor, consistent with the evidence that this region bears the cognate deoxyribonucleic acid (DNA) consensus sequences. These data indicate that Contactin-1 expression is dependent upon EBF factors, suggesting that the Cntn1 gene belongs to the expanding regulatory cascade driven by these transcriptional regulators so that changes in its activation may contribute to the phenotype of Ebf2 null mutant mice.
