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Violations of the 12/23 rule at the mouse immunoglobulin kappa locus, including Vk-Vk rearrangement

March 9, 2010

The ability of the adaptive immune system to recognize an
immense range of antigens stems fromthe process of V(D)J recombination
at the B cell and T cell antigen receptor loci. Each
immunoglobulin (Ig) receptor gene segment is flanked by a recombination
signal sequence (RSS) consisting of conserved heptamer
and nonamer sequences separated by either a 12 or a 23 base pair
spacer (12-RSS or 23-RSS, respectively). Classically, recombination
requires a pair of RSSs with dissimilar spacers (the “12/23 rule”)
(Sakano et al., 1979; Tonegawa, 1983). Previous investigations of
the 12/23 rule have focused primarily on in vitro assays using extrachromosomal
rearrangement substrates (Hesse et al., 1987; Hiom
and Gellert, 1998; Lieber et al., 1988; van Gent et al., 1996). A few
12/23 rule violations have been reported in vivo (Hiramaet al., 1991;
Langerak et al., 2004; Shimizu et al., 1991), but such rearrangements
are generally deemed quite rare, unless the immune system
is forced to use incompatible RSSs (Koralov et al., 2005).
After encountering several peculiar k rearrangements in unrelated
experiments,we set out to molecularly characterize the range
of 12/23 rule violations seen at the Igk locus in vivo. The Igk locus
is well suited for this analysis because of its large size and ability
to undergo inversional rearrangement, with the retention of signal
joints and prior rearrangement coding joints on the chromosome
(Feddersen and Van Ness, 1985; Shapiro andWeigert, 1987). Using
a degenerate Vk primer, we characterized 14 independent Vk-Vk
fusions from spleen and splenic hybridoma DNA, of which 13 contained
Vk4 sequences.We also used a semi-quantitative PCR assay
to measure the frequency of Vk-Vk rearrangements in wild type
mice. The data suggest that these rearrangements are infrequent
compared to conventional Vk-Jk rearrangements. The biological
function of these aberrant rearrangements is unknown.

...
 
Read the full article here
 
Source lupusresearch.org


Violations of the 12/23 rule at the mouse immunoglobulin kappa locus, including Vk-Vk rearrangement

March 9, 2010

The ability of the adaptive immune system to recognize an
immense range of antigens stems fromthe process of V(D)J recombination
at the B cell and T cell antigen receptor loci. Each
immunoglobulin (Ig) receptor gene segment is flanked by a recombination
signal sequence (RSS) consisting of conserved heptamer
and nonamer sequences separated by either a 12 or a 23 base pair
spacer (12-RSS or 23-RSS, respectively). Classically, recombination
requires a pair of RSSs with dissimilar spacers (the “12/23 rule”)
(Sakano et al., 1979; Tonegawa, 1983). Previous investigations of
the 12/23 rule have focused primarily on in vitro assays using extrachromosomal
rearrangement substrates (Hesse et al., 1987; Hiom
and Gellert, 1998; Lieber et al., 1988; van Gent et al., 1996). A few
12/23 rule violations have been reported in vivo (Hiramaet al., 1991;
Langerak et al., 2004; Shimizu et al., 1991), but such rearrangements
are generally deemed quite rare, unless the immune system
is forced to use incompatible RSSs (Koralov et al., 2005).
After encountering several peculiar k rearrangements in unrelated
experiments,we set out to molecularly characterize the range
of 12/23 rule violations seen at the Igk locus in vivo. The Igk locus
is well suited for this analysis because of its large size and ability
to undergo inversional rearrangement, with the retention of signal
joints and prior rearrangement coding joints on the chromosome
(Feddersen and Van Ness, 1985; Shapiro andWeigert, 1987). Using
a degenerate Vk primer, we characterized 14 independent Vk-Vk
fusions from spleen and splenic hybridoma DNA, of which 13 contained
Vk4 sequences.We also used a semi-quantitative PCR assay
to measure the frequency of Vk-Vk rearrangements in wild type
mice. The data suggest that these rearrangements are infrequent
compared to conventional Vk-Jk rearrangements. The biological
function of these aberrant rearrangements is unknown.

...
 
Read the full article here
 
Source lupusresearch.org



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