The MafA Transcription Factor Becomes Essential to Islet b-Cells Soon After Birth Diabetes 2014;63:1994–2005 | DOI: 10.2337/db13-1001

are expressed with distinct spatial–temporal patterns in rodent islet cells. Analysis of Mafa2/2 and pancreas-specific MafaΔpanc deletion mutant mice demon-strated a primary role for MafA in adult b-cell activity, different from the embryonic importance of MafB. Our interests here were to precisely define when MafA be-came functionally significant to b-cells, to determine how this was affected by the brief period of postnatal MafB production, and to identify genes regulated by MafA during this period. We found that islet cell orga-nization, b-cell mass, and b-cell function were influ-enced by 3 weeks of age in MafaDpanc mice and compromised earlier in MafaDpanc;Mafb+/2 mice. A combination of genome-wide microarray profiling, electron microscopy, and metabolic assays were use