Short interspersed repetitive elements (SINEs) are highly repeated sequences that account for a significant proportion of many eukaryotic genomes and are usually considered "junk DNA". However, we previously discovered that many AmnSINE1 loci are evolutionarily conserved across mammalian genomes, suggesting that they may have acquired significant functions involved in controlling mammalian-specific traits. Notably, we identified the AS021 SINE locus, located 390 kbp upstream of Satb2. Using transgenic mice, we showed that this SINE displays specific enhancer activity in the developing cerebral cortex. The transcription factor Satb2 is expressed by cortical neurons extending axons through the corpus callosum and is a determinant of callosal versus subcortical projection. Mouse mutants reveal a crucial function for Sabt2 in corpus callosum formation. In this study, we compared the enhancer activity of the AS021 locus with Satb2 expression during telencephalic development in the mouse. First, we showed that the AS021 enhancer is specifically activated in early-born Satb2(+) neurons. Second, we demonstrated that the activity of the AS021 enhancer recapitulates the expression of Satb2 at later embryonic and postnatal stages in deep-layer but not superficial-layer neurons, suggesting the possibility that the expression of Satb2 in these two subpopulations of cortical neurons is under genetically distinct transcriptional control. Third, we showed that the AS021 enhancer is activated in neurons projecting through the corpus callosum, as described for Satb2(+) neurons. Notably, AS021 drives specific expression in axons crossing through the ventral (TAG1(-)/NPY(+)) portion of the corpus callosum, confirming that it is active in a subpopulation of callosal neurons. These data suggest that exaptation of the AS021 SINE locus might be involved in enhancement of Satb2 expression, leading to the establishment of interhemispheric communication via the corpus callosum, a eutherian-specific brain structure.
Pubmed ID: 22174821 RIS Download
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Collection of genome databases for vertebrates and other eukaryotic species with DNA and protein sequence search capabilities. Used to automatically annotate genome, integrate this annotation with other available biological data and make data publicly available via web. Ensembl tools include BLAST, BLAT, BioMart and the Variant Effect Predictor (VEP) for all supported species.
View all literature mentionsTool used to design PCR primers from DNA sequence - often in high-throughput genomics applications. It does everything from mispriming libraries to sequence quality data to the generation of internal oligos.
View all literature mentionsPortal to interactively visualize genomic data. Provides reference sequences and working draft assemblies for collection of genomes and access to ENCODE and Neanderthal projects. Includes collection of vertebrate and model organism assemblies and annotations, along with suite of tools for viewing, analyzing and downloading data.
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View all literature mentionsMus musculus with name C57BL/6J from IMSR.
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