Enables guanine/thymine mispair binding activity. Acts upstream of or within maintenance of DNA repeat elements. Predicted to be part of MutSalpha complex. Predicted to be active in nucleus. Is expressed in alar plate midbrain region; immature eye; nervous system; and pharyngeal arch 3-7 skeleton. Human ortholog(s) of this gene implicated in several diseases, including Lynch syndrome (multiple); gastrointestinal system cancer (multiple); lung cancer (multiple); mismatch repair cancer syndrome; and transitional cell carcinoma. Orthologous to human MSH2 (mutS homolog 2).