The exon 17 promoter sequence of the GR gene contains guanine-cytosine nucleotides, so-called GC boxes (GCGGGGGCG), which form the core consensus site (ie, a DNA binding site) for NGFIA (Figure 2).86 Thus, increases in NGFIA induced by maternal LG could increase transcription from the exon 17 promoter leading to increased GR mRNA. We previously found that handling increased the binding of NGFIA to a promoter sequence for the human GR promoter containing an NGFIA consensus sequence. Since neonatal handling increases maternal LG, these finding suggest that naturally occurring variations in maternal behavior might regulate GR expression in neonatal offspring through a 5HT-induced increase in NGFIA expression, and the subsequent binding of NGFIA to the exon 17 promoter. Recent findings support this idea, including studies using chromatin immunoprecipitation (ChIP) assay in which the in vivo formation of protein-DNA complexes are examined using cross-linking with paraformaldehyde perfusion and subsequent precipitation from soluble hippocampal samples using specific antibodies. Protein binding, defined by the specificity of the antibody, to specific DNA sequences is then quantified following polymerase chain reaction (PCR) amplification with targeted primers
