Goosecoid-like (Gscl), a candidate gene for velocardiofacial syndrome, is not essential for normal mouse development

Velocardiofacial syndrome (VCFS) and DiGeorge syndrome (DGS) are characterized by a wide spectrum of abnormalities, including conotruncal heart defects, velopharyngeal insufficiency, craniofacial anomalies and learning disabilities, In addition, numerous other clinical features have been described, including frequent psychiatric illness. Hemizygosity for a 1.5-3 Mb region of chromosome 22q11 has been detected in >80% of VCFS/DGS patients. It is thought that a developmental field defect is responsible for many of the abnormalities seen in these patients and that the defect occurs due to reduced levels of a gene product active in early embryonic development. Goosecoid-like (GSCL) is a homeobox gene which is present in the VCFS/DGS commonly deleted region. The mouse homolog, Gscl, is expressed in mouse embryos as early as E8.5. Gscl is related to Goosecoid (Gsc), a gene required for proper craniofacial development in mice. GSCL has been considered an excellent candidate for contributing to the developmental defects in VCFS/DGS patients. To investigate the role of Goosecoid-like in VCFS/DGS etiology, we disrupted the Gscl gene in mouse embryonic stem cells and produced mice that transmit the disrupted allele. Mice that are homozygous for the disrupted allele appear to be normal and they do not exhibit any of the anatomical abnormalities seen in VCFS/DGS patients. RNA in situ hybridization to mouse embryo sections revealed that Gscl is expressed at E8.5 in the rostral region of the foregut and at E11.5 and E12.5 in the developing brain, in the pens region and in the choroid plexus of the fourth ventricle. Although the gene inactivation experiments indicate that haploinsufficiency for GSCL is unlikely to be the sole cause of the developmental field defect thought to be responsible for many of the abnormalities in VCFS/DGS patients, its localized expression during development could suggest that hemizygosity for GSCL, in combination with hemizygosity for other genes in 22q11, contributes to some of the developmental defects as well as the behavioral anomalies seen in these patients. The mice generated in this study should help in evaluating these possibilities.