Mice that are homozygous for the targeted mutation are viable, fertile, normal in size and do not display any gross physical or behavioral abnormalities. No gene product (mRNA or protein) is detected. Although lymphocyte development appears unremarkable, irregularities are observed in lymphocyte trafficking. Tail-injected lymphocytes derived from null animals exhibit an impaired ability to traffic to peripheral lymph nodes, and to a much greater degree, the thymus. Transcription and translation of the targeted allele subsequently lead to the synthesis of the lacZ protein under control of the 5' regulatory elements of the endogenous locus in all cells and tissues normally expressing one or several of the CD44 isoforms.
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. 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.
