NIPBL and Cornelia de Lange syndrome: We show here that mice heterozygous for a gene-trap mutation upstream of the first coding exon of Nipbl displayed many features of human CdLS, including pre- and postnatal growth retardation, cardiac septal defects, delayed bone development, lean body habitus, microbrachycephaly with characteristic craniofacial changes, behavioral disturbances, ophthalmological abnormalities, cerebellar hypoplasia, and hearing deficits (Figures 1–, , 4, Table S1, Videos S1, S2, S3, S4, S5).