The detailed entries of the Imprinted Gene Catalogue database were created by Benjamin Tycko, Columbia University, New York and are updated by Ian Morison


Detailed entry for Gene:

(see also, Gnas1, Nesp)


Human Chr20q13
Mouse Chr2 (distal)




The Xlas gene is embedded in the Gnas1 locus and alternative splicing/promoter usage produces the Xlas mRNA; for a review, see (Lalande M, 2001). The maternal allele is repressed and the paternal allele is active (Hayward BE et al, 1998; Hayward BE et al, 1998).

Gene Product:

Xl-alpha-s protein denotes an "extra-large" (78 kDa) form of the stimulatory subunit of the major heterotrimeric G-protein, Gs. A third protein, called ALEX, is translated from an alternative open reading frame within an Xlas exon. The function of ALEX is not known, but it was reported to bind to the cytoplasmic domain of the Xl-alpha-s protein (Klemke M et al, 2001).

Functional Data:

Xl-alpha-s is a cytoplasmic membrane-associated protein with high expression in neuroendocrine cells (Pasolli HA et al, 2001). The Xl-alpha-s and Gs-alpha (GNAS1) signaling proteins, which arise from the same locus, share sequences and could in principal converge on same effector: adenylyl cyclase. However, they appear to have different response properties to hormonal stimulation (Klemke M et al, 2000).


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