KITLG and macrocytic anemia: Homozygous mutation of the mouse Kitl results in embryonic death due to severe macrocytic anemia, whereas heterozygous mutant animals are viable but manifest a wide spectrum of abnormalities including a variable extent of macrocytic anemia, a reduced number of mast cells, and reduced pigmentation including white spotting or a gray color of fur (Sarvella and Russell 1956; Broudy 1997).