Kaminski H J, Fenstermaker R A, Abdul-Karim F W, Clayman J, Ruff R L
Department of Neurology 127W, Cleveland Veterans Affairs Medical Center, OH 44106.
Muscle Nerve. 1993 Dec;16(12):1332-7. doi: 10.1002/mus.880161210.
It is controversial whether acetylcholine receptors (AChR) or AChR-like proteins exist in human thymus. To evaluate this question we isolated RNA from paraffin-embedded thymic tissue of 5 myasthenics and 5 nonmyasthenics. RNA was subjected to reverse transcription followed by polymerase chain reaction (RT-PCR) using primers specific for beta-actin, subunits of the fetal- and adult-type AChR, and Myf-4, a gene product which regulates AChR expression in muscle. beta-Actin transcripts were identified in specimens from 8 of 10 patients. In these 8 patients alpha- and epsilon-subunit transcripts were identified. 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 subunits of the adult-type AChR are expressed in thymic tissue by mechanisms not involving Myf-4. AChR subunits in pathological thymus may provide a target for immune attack in MG. However, as AChR subunits were found in thymus tissue from myasthenics and nonmyasthenics, the presence of AChR subunits in thymus alone is not sufficient to produce myasthenia gravis.
人类胸腺中是否存在乙酰胆碱受体（AChR）或AChR样蛋白存在争议。为评估这个问题，我们从5例重症肌无力患者和5例非重症肌无力患者的石蜡包埋胸腺组织中分离RNA。RNA进行逆转录，随后使用针对β-肌动蛋白、胎儿型和成人型AChR亚基以及Myf-4（一种调节肌肉中AChR表达的基因产物）的特异性引物进行聚合酶链反应（RT-PCR）。在10例患者中的8例标本中鉴定出β-肌动蛋白转录本。在这8例患者中鉴定出α和ε亚基转录本。这些转录本的存在与胸腺病理学或临床表现无关。未发现γ亚基（胎儿型AChR特异性）或Myf-4转录本。我们的结果表明，成人型AChR亚基的mRNA在胸腺组织中通过不涉及Myf-4的机制表达。病理性胸腺中的AChR亚基可能为重症肌无力的免疫攻击提供靶点。然而，由于在重症肌无力患者和非重症肌无力患者的胸腺组织中均发现了AChR亚基，仅胸腺中存在AChR亚基不足以导致重症肌无力。
