This ENU-induced mutation was isolated in a screen at the University of Pittsburgh. It is a subline of b2b3260Clo. The molecular lesion is a G to A substitution at nucleotide +1 after coding nucleotide 3100 (c.3100+1G>A, NM_001033385) in intron 27. This changes splice donor site G-GT to G-AT (which is assumed to be inactive).