Mice homozygous for the Tlx1tm1Sjk targeted mutation on this NOD congenic background do not differ in diabetes incidence from standard NOD controls and thymic T and B cell profiles are normal even though these homozygotes are asplenic. The outward appearance looks like that of the NOD host background, with no obvious limb abnormalities (D.V. Serreze, personal communication). Tlx1tm1Sjk homozygotes have been finely characterized on other genetic backgrounds and found to lack a spleen; however, all other internal organs were found to be normal. Characteristics reported included: polydactyly or oligodactyly of the hindlimbs, tibial hemimelia, and sometimes reduction of the femur and pubic element of the pelvic girdle. Pharyngeal and mastication muscles derived from the branchial arches were reported to be present and anatomically normal homozygotes had normal cranial ganglia morphology and position and normal cranial motor nuclei function. Also reported were normal numbers of RBCs but increased numbers of WBCs, including neutrophils and lymphocytes. The B-cell and T-cell profile was described as normal in the thymus, lymph nodes and peripheral blood. Many erythrocytes had nuclear fragments (Howell-Jolly bodies).
In an attempt to offer alleles on well-characterized or multiple genetic backgrounds, alleles are frequently moved to a genetic background different from that on which an allele was first characterized. This is the case for the strain above. It should be noted that the phenotype could vary from that originally described. We will modify the strain description if necessary as published results become available.
