Transcriptional activator of GFAP, essential for proper brain development (PubMed:15632069, PubMed:30388402). Recognizes and binds the palindromic sequence 5'-TTGGCNNNNNGCCAA-3' present in viral and cellular promoters and in the origin of replication of adenovirus type 2. These proteins are individually capable of activating transcription and replication (PubMed:30388402). Binds DNA as a homodimer. Highest expression in lung, skeletal muscle and heart. Lower levels in liver, kidney and brain. Very low levels in testis and spleen. The 9aaTAD motif is a transactivation domain present in a large number of yeast and animal transcription factors. NFIB knockout results in failure of lung maturation, and severe defects in development of the corpus callosum, specific midline glial populations, the hippocampus and the pons. GFAP expression is reduced in brains of NFIB-null mice (PubMed:15632069). Conditional NFIB knockdown in the telencephalon results in significant enlargement of the cerebral cortex with preservation of overall brain structure and inter-hemispheric connectivity (PubMed:30388402). Belongs to the CTF/NF-I family.