Analysis of Muscle Dystrophin mRNA in Duchenne/Becker Type Muscular Dystrophy Patients with a Partial Genomic DNA Deletions
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概要
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Duchenne型(DMD)およびBecker型(BMD)筋ジストロフィー患者におけるジストロフィン遺伝子部分欠失がmRNAレベルではどのようになっているのかを明らかにするため、RT-PCRを用いて,欠失を示すDMD11例およびBMD6例について骨格筋のジストロフィンmRNAの分析を行つた.さらに,DMD3例とBMD5例について,semi-nestedPCRによりジストロフィンmRNAを定量した.コントロールに比較して,DMD/BMD患者のジストロフィンmRNAはいずれも有意に減少していたが(p<0.05),DMDとBMDとの間には有意差が認められなかつた.DMD/BMD患者17例について,ジストロフィン遺伝子の三つの領域(欠失を含む領域,欠失の上流側,下流側)をそれぞれ増幅した.欠失を含む領域の転写産物が得られ,その塩基配列を分析した.16例において,DMD1例では他のDMDに比べ、臨床的重症度に差はなかつたが,RT-PCR産物は得られず,転写における障害と推測された.他のDMD1例では,リンパ球のDNAの欠失と骨格筋のmRNAにおける欠失領域の不一致を認めた.このことはDNA診断において,プライマー領域の欠失により,欠失していないexonを欠失していると誤る可能性を示唆した.別のDMD1例では,骨格筋のmRNAとリンパ球のmRNAの欠失領域に不一致があり,これはsomatic mosaicismによるものと考えられた.DMD/BMDの患者におけるジストロフィン遺伝子欠失の分子レベルにおけるメカニズムを解明するため,mRNAの分析は重要と考えられる.In order to elucidate the effects of dystrophin gene deletions on the mRNA levels in the Duchenne and Becker muscular dystrophy, we analyzed human muscle dystrophin mRNA from eleven Duchenne muscular dystrophy (DMD) and six Becker muscular dystrophy (BMD) patients, with internal deletions of the dystrophin gene, using RT-PCR. We also quantified the resultant transcripts by means of semi-nested PCR to estimate the dystrophin mRNA in four BMD and three DMD cases. We found that the quantities of muscle dystrophin mRNA were drastically decreased in DMD and BMD patients as compared with in control subjects (p < 0.05), but that there was no significant difference between DMD and BMD. In each case, three regions of the DMD gene (the deletion-containing region, and the upstream and downstream regions) were amplified, and we focused on the deletion boundary regions by sequencing the PCR products. Truncated transcripts were found in 16 cases, while in the remaining case (DMD), no RT-PCR product was amplified for either muscle or lymphocytes, and thus transcription was assumed to be disturbed. We detected a difference between the muscle mRNA and lymphocyte DNA deletions in a patient who died of a rhabdomyosarcoma. In this case, there was an apparent deletion of exon 48 in the lymphocyte DNA, while only 15 by of the 3' region of exon 48 was deleted from the muscle mRNA. This raises the possibility that DNA diagnosis can miss a deletion. Another DMD case showed two distinct deletion patterns in muscle versus lymphocyte mRNA due to somatic mosaicism. Thus, it is important to analyze mRNA to clarify the molecular mechanisms of DMD/BMD.
- 1998-09-25