HGNC Approved Gene Symbol: GAS1
Cytogenetic location: 9q21.33 Genomic coordinates (GRCh38): 9:86,944,362-86,947,506 (from NCBI)
Growth arrest-specific genes were cloned from mRNAs unique to quiescent, serum-starved NIH 3T3 mouse fibroblasts (Schneider et al., 1988).
Using the mouse sequence as probe, Del Sal et al. (1994) cloned GAS1 from a liver cDNA library, and they obtained the full-length cDNA by 5-prime RACE of human embryo fibroblast mRNA. The deduced 345-amino acid protein contains 2 putative transmembrane domains, an RGD consensus recognition sequence, and 1 potential N-glycosylation site. The human and mouse proteins share 82% sequence identity. In vitro translation resulted in a protein with an apparent molecular mass of about 45 kD.
Stebel et al. (2000) demonstrated that the GAS1 protein undergoes cotranslational modifications within the endoplasmic reticulum. Modifications consist of signal peptide cleavage, N-linked glycosylation, and glycosylphosphatidylinositol anchor addition. Immunoelectron microscopy of resting mouse fibroblasts found Gas1 randomly distributed over the outer leaflet of the plasma membrane. Upon antibody-induced clustering, Gas1 relocalized to caveolae.
Del Sal et al. (1994) demonstrated that overexpression of the human GAS1 gene is able to block cell proliferation in lung and bladder carcinoma cell lines, but not in an osteosarcoma cell line or in an adenovirus-type-5 transformed cell line. Del Sal et al. (1992) had previously shown that simian virus 40-transformed NIH 3T3 cells are also refractory to murine GAS1 overexpression, suggesting that the retinoblastoma and/or p53 gene products have an active role in mediating the growth-suppressing effect of GAS1.
Martinelli and Fan (2007) found that Gas1 positively regulated hedgehog (see SHH; 600725) signaling in developing mouse and chicken, an effect particularly noticeable at regions where hedgehog acted at low concentrations. Using in vitro cell culture and in ovo electroporation assays, they demonstrated that Gas1 acted cooperatively with Patched-1 (PTCH1; 601309) for hedgehog binding and enhanced signaling activity in a cell-autonomous manner.
Allen et al. (2007) reported findings similar to those of Martinelli and Fan (2007). They showed that Gas1 and Cdo (CDON; 608707) cooperated to promote Shh signaling during neural tube patterning and craniofacial and vertebral development in mouse.
Using 3-dimensional cultures of weakly metastatic B16-F0 mouse melanoma cells and a genomewide RNA interference screen, Gobeil et al. (2008) identified Gas1 as a candidate metastasis suppressor. Gas1 was downregulated in B16-F10 cells, a highly metastatic counterpart of B16-F0 cells, and its knockdown in B16-F0 cells increased metastatic potential without affecting primary cell growth. Gas1 expression in B16-F0 cells suppressed metastasis of cells in lung following tail-vein injection by promoting apoptosis at the secondary site. Western blot analysis showed that expression of GAS1 was high in the UACC-257 cell line derived from a primary human melanoma, but was markedly reduced in melanoma cell lines derived from metastases of lymph node, lung, and skin. Knockdown of GAS1 in UACC-257 cells increased their ability to form colonies in 3-dimensional cultures. Gobeil et al. (2008) concluded that GAS1 is metastasis suppressor.
Webb et al. (1992) mapped the Gas1 gene to mouse chromosome 13 by in situ hybridization. Colombo et al. (1992) showed linkage of Gas1 to markers on mouse chromosome 13 in a region that contains 8 loci that are conserved in human 5q, mainly 5q11-q14. Gas1 is close to the IL9 gene (146931), for example. On this basis, Webb et al. (1992) predicted that the GAS1 gene in man is located on 5q. However, the prediction proved not to be true. Evdokiou et al. (1993) localized the human GAS1 gene to 9q21.3-q22 by tritium-labeled in situ hybridization. DNA from human-rodent somatic cell hybrids was used to verify the location of GAS1 to human chromosome 9. They stated that GAS1 was the first gene to be mapped to both human chromosome 9 and mouse chromosome 13. The location of GAS1 at a site of deletion in myeloid malignancies, together with the demonstration that GAS1 suppresses DNA synthesis, suggested that it is a tumor suppressor gene. By in situ hybridization, Del Sal et al. (1994) mapped the GAS1 gene to 9q21.3-q22.1 in a region considered to be a fragile site. Observations suggesting involvement of this area in bladder carcinoma were cited.
Combining studies of cell surface binding, in vitro activity, and mouse limb bud explants, Martinelli and Fan (2009) demonstrated that murine Shh residues tyr81, glu90, asn116, and asp132 form part of a contiguous Gas1-Shh interface, and that Gas1 positively regulates Shh signaling. A constructed Shh N116K mutant, which corresponds to the holoprosencephaly-3 (HPE3; 142945)-associated SHH mutation N115K (600725.0020), caused markedly decreased binding to Gas1, resulting in decreased Shh signaling. These findings indicated that HPE due to the N115K mutation results from an inability of mutant SHH to bind to GAS1 normally, thus interrupting positive effect of GAS1. Martinelli and Fan (2009) suggested that mutations in the GAS1 gene may act as possible modifiers of HPE.
In 4 Brazilian patients with HPE or HPE-like phenotype, Ribeiro et al. (2010) identified 4 different heterozygous nonsynonymous variants in the GAS1 gene that were predicted to be possibly pathogenic. Two patients carried only a heterozygous GAS1 variant (T200R, 139185.0001 and G259E, 139185.0002, respectively), whereas the other 2 patients also carried heterozygous missense mutations in the SHH gene. The parents of the patient with the T200R variant were not available for study; molecular analysis of the GAS1 gene was not performed in the parents of the patient with the G259E variant. The authors suggested that variants in the GAS1 gene may confer susceptibility to the development of HPE or may act as modifiers for HPE in conjunction with mutations in other genes.
Pineda-Alvarez et al. (2012) identified 5 different heterozygous variants in the GAS1 gene in 5 of 394 patients with clinical findings within the holoprosencephalic phenotypic spectrum. However, 2 of the variants (L6V and G320C) were predicted to be benign, 4 of the 5 variants were inherited from an unaffected parent, and 1 patient had an additional pathogenic mutation in the SHH gene. In vitro functional expression studies of 4 of the variants, as well as the 2 reported by Ribeiro et al. (2010), showed that 1 (T200R, 139185.0001) had 95% reduced binding to SHH, and 4 variants had a 5 to 25% reduction in SHH binding, consistent with hypomorphic alleles. Pineda-Alvarez et al. (2012) concluded that variations in the GAS1 gene can function as modifiers of other Hedgehog-related gene products. The authors speculated that hypomorphic GAS1 alleles may contribute to phenotypic variability in patients who have mutations in other HPE-related genes, consistent with a multiple-hit hypothesis for the pathogenesis of HPE.
Seppala et al. (2007) generated Gas1 -/- mice and observed microform holoprosencephaly (see 236100), including midfacial hypoplasia, premaxillary incisor fusion, and cleft palate, in addition to severe ear defects; however, the forebrain remained grossly intact. These defects were associated with a loss of Shh signaling in cells at a distance from the source of transcription, and loss of a single Shh allele on a Gas1 -/- background significantly exacerbated the midline craniofacial phenotype. Seppala et al. (2007) concluded that GAS1 and SHH interact and that GAS1 is a potential locus for human craniofacial malformations.
This variant is classified as a variant of unknown significance because its contribution to a holoprosencephaly phenotype has not been confirmed.
In a Brazilian girl with semilobar holoprosencephaly (see 236100), Ribeiro et al. (2010) identified a heterozygous 599C-G transversion in the GAS1 gene, resulting in a thr200-to-arg (T200R) substitution. The patient had severe neurodevelopmental delay, flat face, upslanted palpebral fissures, prominent eyes, maxillary hypoplasia, low nasal bridge, broad nose, absent columella, and hypoplastic prolabium/premaxilla with a cleft lip/palate. She also had generalized seizures and abnormal regulation of body temperature since birth. The parents were not available for study. The variant was not found in the dbSNP database, and the patient did not carry mutations in other known HPE-related genes (SHH, GLI2, PTCH, SIX3, and TGIF). The variant was predicted to be possibly pathogenic.
In vitro functional expression assays in COS cells by Pineda-Alvarez et al. (2012) showed that the T200R variant GAS1 protein had a 95% loss of SHH (600725)-binding affinity compared to wildtype, despite normal protein expression. The findings were consistent with a loss of function. The substitution is located in the second cysteine-rich domain, which is important in receptor binding function.
Hamosh (2017) noted that the T200R variant was identified in 1 Ashkenazi Jewish and 1 Finnish patient in the gnomAD database (May 22, 2017).
This variant is classified as a variant of unknown significance because its contribution to a holoprosencephaly phenotype has not been confirmed.
In a Brazilian girl with mild holoprosencephaly (see 236100), Ribeiro et al. (2010) identified a heterozygous 775G-A transition in the GAS1 gene, resulting in a gly259-to-glu (G259E) substitution. The patient had flat face, flat nasal bridge, prominent and large eyes, maxillary hypoplasia, hypoplastic nasal septum with nasal depression, absent columella, hypoplastic prolabium/premaxilla with a cleft lip/palate, and normal psychomotor development. The variant was not found in the dbSNP database, and the patient did not carry mutations in other known HPE-related genes (SHH, GLI2, PTCH, SIX3, and TGIF). The GAS1 gene was not analyzed in the patient's parents. The variant was predicted to be possibly pathogenic.
In vitro functional expression assays in COS cells by Pineda-Alvarez et al. (2012) showed that the G259E variant GAS1 protein had a 10% loss of SHH (600725)-binding affinity compared to wildtype, indicating a hypomorphic allele. Pineda-Alvarez et al. (2012) stated that the 775G-A transition corresponds to a gly259-to-arg (G259R) substitution.
Allen, B. L., Tenzen, T., McMahon, A. P. The hedgehog-binding proteins Gas1 and Cdo cooperate to positively regulate Shh signaling during mouse development. Genes Dev. 21: 1244-1257, 2007. [PubMed: 17504941] [Full Text: https://doi.org/10.1101/gad.1543607]
Colombo, M. P., Martinotti, A., Howard, T. A., Schneider, C., D'Eustachio, P., Seldin, M. F. Localization of growth arrest-specific genes on mouse chromosomes 1, 7, 8, 11, 13, and 16. Mammalian Genome 2: 130-134, 1992. [PubMed: 1347472] [Full Text: https://doi.org/10.1007/BF00353861]
Del Sal, G., Collavin, L., Ruaro, M. E., Edomi, P., Saccone, S., Della Valle, G., Schneider, C. Structure, function, and chromosome mapping of the growth-suppressing human homologue of the murine gas1 gene. Proc. Nat. Acad. Sci. 91: 1848-1852, 1994. [PubMed: 8127893] [Full Text: https://doi.org/10.1073/pnas.91.5.1848]
Del Sal, G., Ruaro, M. E., Philipson, L., Schneider, C. The growth arrest-specific gene, gas1, is involved in growth suppression. Cell 70: 595-607, 1992. [PubMed: 1505026] [Full Text: https://doi.org/10.1016/0092-8674(92)90429-g]
Evdokiou, A., Webb, G. C., Peters, G. B., Dobrovic, A., O'Keefe, D. S., Forbes, I. J., Cowled, P. A. Localization of the human growth arrest-specific gene (GAS1) to chromosome bands 9q21.3-q22, a region frequently deleted in myeloid malignancies. Genomics 18: 731-733, 1993. [PubMed: 8307588] [Full Text: https://doi.org/10.1016/s0888-7543(05)80388-x]
Gobeil, S., Zhu, X., Doillon, C. J., Green, M. R. A genome-wide shRNA screen identifies GAS1 as a novel melanoma metastasis suppressor gene. Genes Dev. 22: 2932-2940, 2008. [PubMed: 18981472] [Full Text: https://doi.org/10.1101/gad.1714608]
Hamosh, A. Personal Communication. Baltimore, Md. May 22, 2017.
Martinelli, D. C., Fan, C.-M. Gas1 extends the range of hedgehog action by facilitating its signaling. Genes Dev. 21: 1231-1243, 2007. [PubMed: 17504940] [Full Text: https://doi.org/10.1101/gad.1546307]
Martinelli, D. C., Fan, C.-M. A sonic hedgehog missense mutation associated with holoprosencephaly causes defective binding to GAS1. J. Biol. Chem. 284: 19169-19172, 2009. [PubMed: 19478089] [Full Text: https://doi.org/10.1074/jbc.C109.011957]
Pineda-Alvarez, D. E., Roessler, E., Hu, P., Srivastava, K., Solomon, B. D., Siple, C. E., Fan, C.-M., Muenke, M. Missense substitutions in the GAS1 protein present in holoprosencephaly patients reduce the affinity for its ligand, SHH. Hum. Genet. 131: 301-310, 2012. [PubMed: 21842183] [Full Text: https://doi.org/10.1007/s00439-011-1078-6]
Ribeiro, L. A., Quiezi, R. G., Nascimento, A., Bertolacini, C. P., Richieri-Costa, A. Holoprosencephaly and holoprosencephaly-like phenotype and GAS1 DNA sequence changes: Report of four Brazilian patients. Am. J. Med. Genet. 152A: 1688-1694, 2010. [PubMed: 20583177] [Full Text: https://doi.org/10.1002/ajmg.a.33466]
Schneider, C., King, R. M., Philipson, L. Genes specifically expressed at growth arrest of mammalian cells. Cell 54: 787-793, 1988. [PubMed: 3409319] [Full Text: https://doi.org/10.1016/s0092-8674(88)91065-3]
Seppala, M., Depew, M. J., Martinelli, D. C., Fan, C.-M., Sharpe, P. T., Cobourne, M. T. Gas1 is a modifier for holoprosencephaly and genetically interacts with Sonic hedgehog. J. Clin. Invest. 117: 1575-1584, 2007. [PubMed: 17525797] [Full Text: https://doi.org/10.1172/JCI32032]
Stebel, M., Vatta, P., Ruaro, M. E., Del Sal, G., Parton, R. G., Schneider, C. The growth suppressing gas1 product is a GPI-linked protein. FEBS Lett. 481: 152-158, 2000. [PubMed: 10996315] [Full Text: https://doi.org/10.1016/s0014-5793(00)02004-4]
Webb, G. C., Cowled, P. A., Evdokiou, A., Ford, J. H., Forbes, I. J. Assignment, by in situ hybridization, of the growth arrest-specific gene, Gas-1, to mouse chromosome 13, bands B3-C2. Genomics 14: 548-549, 1992. [PubMed: 1427878] [Full Text: https://doi.org/10.1016/s0888-7543(05)80267-8]