TY - JOUR
T1 - The genetic basis of the phase variation repertoire of lipopolysaccharide immunotypes in Neisseria meningitidis
AU - Jennings, Michael P.
AU - Srikhanta, Yogitha N.
AU - Moxon, E. Richard
AU - Kramer, Marco
AU - Poolman, Jan T.
AU - Kuipers, Betsy
AU - Van Der Ley, Peter
PY - 1999/1/1
Y1 - 1999/1/1
N2 - Neisseria meningitidis strains express a diverse range of lipopolysaccharide (LPS) structures that have been classified into 12 immunotypes. A feature of meningococcal LPS is the reversible, high-frequency switching of expression (phase variation) of terminal LPS structures. A number of studies are strongly suggestive of a key role for these terminal structures, and their phase-variable expression, in pathogenesis. In a previous study, a locus of three LPS biosynthetic genes, lgtABE, involved in the biosynthesis of one of these terminal structures, lacto-N-neotetraose, was described. The molecular mechanism of phase-variable expression of this structure is by high-frequency mutation in a homopolymeric tract of C residues in the lgtA gene. To investigate the genetic basis of the structural differences between the immunotypes, and the potential for strains to express alternative immunotypes, this locus was examined in all of the immunotype strains. Initially, the lgt locus of strain 126E, an L1 immunotype strain, was cloned and sequenced, revealing two active genes, lgtC and lgtE. The remnants of the lgtA and lgtB genes and an inactive lgtD gene were also present, indicating that the locus may have once contained five active genes, similar to a locus previously reported in Neisseria gonorrhoeae strain F62. Probes based on each of the lgt genes (ABCDE), and the recently reported lgtG gene, were used to determine the presence or absence of lgt genes within individual strains, allowing the prediction of the phase variation repertoire of these strains. Sequencing to determine the nature of homopolymeric tract regions within the lgt genes was carried out to establish the potential for LPS switching. In general, the set of strains examined could be sorted into two distinct groups: one group which phase-vary the α-chain extension via lgtA or lgtC but cannot make β-chain; the second group phase-vary the β-chain extension via lgtG but do not vary α-chain (lacto-N-neotetraose).
AB - Neisseria meningitidis strains express a diverse range of lipopolysaccharide (LPS) structures that have been classified into 12 immunotypes. A feature of meningococcal LPS is the reversible, high-frequency switching of expression (phase variation) of terminal LPS structures. A number of studies are strongly suggestive of a key role for these terminal structures, and their phase-variable expression, in pathogenesis. In a previous study, a locus of three LPS biosynthetic genes, lgtABE, involved in the biosynthesis of one of these terminal structures, lacto-N-neotetraose, was described. The molecular mechanism of phase-variable expression of this structure is by high-frequency mutation in a homopolymeric tract of C residues in the lgtA gene. To investigate the genetic basis of the structural differences between the immunotypes, and the potential for strains to express alternative immunotypes, this locus was examined in all of the immunotype strains. Initially, the lgt locus of strain 126E, an L1 immunotype strain, was cloned and sequenced, revealing two active genes, lgtC and lgtE. The remnants of the lgtA and lgtB genes and an inactive lgtD gene were also present, indicating that the locus may have once contained five active genes, similar to a locus previously reported in Neisseria gonorrhoeae strain F62. Probes based on each of the lgt genes (ABCDE), and the recently reported lgtG gene, were used to determine the presence or absence of lgt genes within individual strains, allowing the prediction of the phase variation repertoire of these strains. Sequencing to determine the nature of homopolymeric tract regions within the lgt genes was carried out to establish the potential for LPS switching. In general, the set of strains examined could be sorted into two distinct groups: one group which phase-vary the α-chain extension via lgtA or lgtC but cannot make β-chain; the second group phase-vary the β-chain extension via lgtG but do not vary α-chain (lacto-N-neotetraose).
KW - lgt genes
KW - Lipooligosaccharide
KW - Lipopolysaccharide
KW - Neisseria meningitidis
KW - Phase variation
UR - http://www.scopus.com/inward/record.url?scp=0032744663&partnerID=8YFLogxK
U2 - 10.1099/00221287-145-11-3013
DO - 10.1099/00221287-145-11-3013
M3 - Article
C2 - 10589709
AN - SCOPUS:0032744663
VL - 145
SP - 3013
EP - 3021
JO - Microbiology-Sgm
JF - Microbiology-Sgm
SN - 1350-0872
IS - 11
ER -