Sj. Greenberg et al., NOVEL COMPOUND TETRANUCLEOTIDE, DINUCLEOTIDE MICROSATELLITE POLYMORPHISM IN THE TUMOR NECROSIS FACTOR-LYMPHOTOXIN LOCUS, Clinical and diagnostic laboratory immunology, 4(1), 1997, pp. 79-84
A polymorphic (TGCG)(n) tetranucleotide repeat was discovered juxtapos
ed to the (GT)(n) dinucleotide repeat that comprises the tumor necrosi
s factor a microsatellite (TNFa) located telomeric to the tumor necros
is factor/lymphotoxin gene cluster. The degree of complexity of this c
ompound tetra-, dinucleotide microsatellite consists of 16 potential a
lleles of combined length ranging from 24 to 54 bp. The pattern of fre
quencies of individual alleles belonging to the compound TNFa microsat
ellite was established from 52 healthy volunteers and was found to be
highly heterogeneous. The data diverges significantly from previously
published statistics that recognized only a simple variable dinucleoti
de tandem repeat. The newly recognized compound tetra-, dinucleotide T
NFa microsatellite polymorphism establishes a more accurate genetic ba
sis to explore potential linkage with disease susceptibility genes loc
ated within this region of the class III major histocompatibility comp
lex. In addition, variable tumor necrosis factor and lymphotoxin produ
ction may reflect the more complex polymorphic nature of this microsat
ellite region. Finally, compound microsatellites probably exist elsewh
ere, throughout the human genome. Recognition of their presence may ha
ve a considerable impact on the validity of past and future microsatel
lite-based genetic analyses.