Myf-4 does not mediate AChR receptor subunit mRNA expression in thymic tissues.
We investigated whether a MyoD gene family member plays a role in the expression of AChR or AChR-like proteins in human thymus. We amplified from thymic tissue, mRNA of subunits of the fetal- and adult-type AChR, and Myf-4, a gene product that appears to regulate AChR expression. RNA extracted from paraffin-embedded thymic tissue of five myasthenics and five nonmyasthenics was subjected to reverse transcription followed by polymerase chain reaction using primers specific for these mRNAs. Thymic RNA from eight of ten patients contained transcripts of the alpha- and epsilon-subunits (specific for the adult-type AChR). Presence of these transcripts did not correlate with thymic pathology or clinical presentation. No gamma-subunit (specific for the fetal-type AChR) or Myf-4 transcripts were found. Our results indicate that mRNA for the adult-type AChR is expressed in thymic tissue and is expressed by mechanisms not involving Myf-4. Thymic AChR subunits may be the primary epitope that initiates the immune response in MG against the adult-type AChR.
Kaminski
H J
HJ
Department of Neurology, Cleveland Veterans Affairs Medical Center, Ohio 44106.
Fenstermaker
R A
RA
Abdul-Karim
F W
FW
Clayman
J
J
Ruff
R L
RL
D000328:Adult; D000368:Aged; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D018006:Myogenic Regulatory Factors; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D012333:RNA, Messenger / Q000235:genetics; D011978:Receptors, Nicotinic / Q000235:genetics*; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009124:Muscle Proteins; D018006:Myogenic Regulatory Factors; D009838:Oligodeoxyribonucleotides; D012333:RNA, Messenger; D011978:Receptors, Nicotinic; C063403:myogenic factor 6