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Articles |
Locus Is Similarly Well Expressed in Mice and Humans
Transgenic mice carrying a 380-kb region of the human immunoglobulin (Ig)
light (L) chain locus in germline configuration were created. The introduced translocus on a yeast artificial chromosome (YAC) accommodates the most proximal Ig
variable region (V) gene cluster, including 15 V
genes that contribute to >60% of
L chains in humans, all J
-C
segments, and the 3' enhancer. HuIg
YAC mice were bred with animals in which mouse Ig
production was silenced by gene targeting. In the
–/– background, human Ig
was expressed by
84% of splenic B cells. A striking result was that human Ig
was also produced at high levels in mice with normal
locus. Analysis of bone marrow cells showed that human Ig
and mouse Ig
were expressed at similar levels throughout B cell development, suggesting that the Ig
translocus and the endogenous
locus rearrange independently and with equal efficiency at the same developmental stage. This is further supported by the finding that in hybridomas expressing human Ig
the endogenous L chain loci were in germline configuration. The presence of somatic hypermutation in the human V
genes indicated that the Ig
-expressing cells function normally. The finding that human
genes can be utilized with similar efficiency in mice and humans implies that L chain expression is critically dependent on the configuration of the locus.
Key Words: human Ig
translocus light chain expression levels pre-B cell activation V gene usage hypermutation
A.V. Popov and X. Zou contributed equally to this work.
Abbreviations used: ES, embryonic stem; Hu, human; N, nonencoded; P, palindromic; PFGE, pulsed-field gel electrophoresis; PNA, peanut agglutinin; PP, Peyer's patch; RACE, rapid amplification of cDNA ends; RSS, recombination signal sequence(s); RT, reverse transcriptase; TdT, terminal deoxyribonucleotide transferase; YAC, yeast artificial chromosome.
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