- 學位論文
努南氏症候群與PTPN11基因之關聯性與遺傳分析
Genetic analysis of PTPN11 gene and its correlation with Noonan syndrome
摘要
努南氏症候群為一種發展異常的疾病同時具有以下特點：特殊的臉型異常、身材矮小，先天性心臟缺陷、骨骼畸形等。將近50%的病人中可發現位於第12對染色體的PTPN11基因有點突變的情形，而導致SHP-2 (src homology region 2-domain phosphatase-2)蛋白的功能增加。我們使用van der Burgt等人於1994年 發表的努南氏症候群評分系統為診斷病人的標準。分析6個病人的PTPN11基因，發現其中5個病人在PTPN11基因有突變的情形。2位病人的突變位於exon 3，2位於exon 8，另一位在exon 12。所有的突變皆是點突變所造成且皆位於胺基酸末端同原體2 [amino-terminal src-homology 2 (N-SH2)]以及酪胺酸蛋白磷酸酶 [protein tyrosine phosphatasec (PTP)]相互作用的位置。五位病人中有3人是偶發的一位是家族遺傳的。病人中帶有182A?蛄 [(Asp61Gly) N-SH-2 domain]突變者有典型的努南氏症候群的症狀。帶有922A?蛄 [(Asn308Asp) (PTP domain)]突變者具有智能發展遲緩的情形。有1403C?袍 [(Thr468Met) (PTP domain)]突變之病人具有明顯的心肌肥厚的情形。而且此病人最初診斷為努南氏症候群，但其突變位點位於LEOPARD症候群好發的位點，且其後並有咖啡牛奶斑的形成，因而認定是LEOPARD症候群。病人中帶有218C?袍 [(Thr73Ile) (N-SH2 domian) 突變者於出生不久即被診斷罹患青少年骨髓單核細胞性白血病 [JMML (juvenile myelomonocytic leukemia)]。不同於以往的研究，本病人的預後十分不好，於出生不久即有嚴重且致命的感染、呼吸衰竭與心臟衰竭的情形發生。努南氏症候群與JMML的關連性可以解釋為因為SHP-2蛋白結構的改變而使RAS系統的訊息傳遞發生問題所致。本研究的主要目的是探討努南氏症候群於PTPN11基因突變位點與臨床表徵的關係。因為PTPN11基因的異常因而會影響RAS-MAPKinase pathway的訊息傳遞，此訊息傳遞路徑與細胞增生、分化以及生存的調控有關。惡性腫瘤的產生與此訊息傳遞受到干擾亦有相關，此常是導因於後天性的體細胞突變所致；最近的研究也發現若於RAS的訊息傳遞鏈上任何一個組成發生生殖細胞的突變時則會導致許多表現型相互重疊與相似的異常，這些疾病被統稱為neuro-cardio-facial-cutaneous 症候群。包括第一型神經纖維瘤(neurofibromatosis type 1)，努南氏症候群(Noonan syndrome)，LEOPARD 症候群，Costello症候群以及cardiofaciocutaneous症候群等，這些疾病都會有不同程度的認知與動作發展遲緩、先天性心臟病、特殊的臉部特徵、身材矮小、皮膚異常表現以及容易產生惡性腫瘤的特異體質。以上皆因RAS-MAPKinase訊息傳遞路徑中之生殖細胞基因發生突變而導致此訊息傳遞路徑產生功能失調所致。無疑的更多的基因異常導致相關的症候群必會陸續被發現，因為仍有許多基因與此訊息傳遞路徑有關，而更多的RAS-MAPKinase訊息傳遞路徑的機轉與惡性腫瘤的關連性也是將來研究的重點。
並列摘要
Noonan syndrome (NS) is a developmental disorder characterized by facial dysmorphia, short stature, cardiac heart defects, and skeletal malformations. In approximately 50% of cases, it is caused by missense mutations in the PTPN11 gene on chromosome 12, resulting in a gain function of the protein SHP-2 (src homology region 2-domain phosphatase-2). In this study, we used NS scoring system developed by van der Burgt et al. in 1994 as diagnostic criteria for our cases. PTPN11 mutation analysis was performed in six NS patients and mutations were found in five of them. Two were in exon 3 and one was in exon 8 and the others was in exon 12. All mutations were missense changes and clustered at the interacting portions of the amino-terminal src-homology 2 (N-SH2: exon 1-3) and protein tyrosine phosphatase (PTP: exon 7-13) domain. Three of them are sporadic and the other is familial NS. No mutation was found in the C-SH2 domain. Patients with NS carried the 922A?蛄 (Asn308Asp) has mild mental retardation. Patient with NS carried the 182 A→G (Asp61Gly) has classic NS symptoms with failure to thrive. Patient with NS carried the 1403C?? T (Thr468Met) has dominant hypertrophic cardiomyopathy. Simultaneously, we find this mutation site is the hot spot of LEOPARD syndrome. Tracing his clinical symptom, the café-au-lait spots developed recent one year and confirme the final diagnosis of LOEPARD syndrome. Patients with NS carried the mutation 218C?袍 (Thr73Ile) has also suffered form juvenile myelomonocytic leukemia (JMML). Unlike the previous studies, her prognosis is very poor and life threatening infection respiratory and heart failure developed shortly after delivery. The correlation between NS and JMML can be explained by the involvement of SHP-2 in RAS-signaling. Our study is to analyze of the PTPN11 gene and it’s correlation with Noonan syndrome. Because the PTPN11 gene mutatin affect the RAS-MAPKinase pathway signalling. The signaling cascade regulates cell proliferation, differentiation and survival. Disturbed RAS signaling in maliganacies is caused by acquired somatic mutations in RAS genes or other compoments of this pathway. Recently, germline mutations in genes coding for different components of the RAS signaling cascade have been recognized as the cause of several phenotypically overlapping disorders, and referred to as the neuro-cardio-facial- cutaneous dyndromes. Neurofibromatosis type 1, Noonan syndrome, LEOPARD, Costello and cardiofaciocutaneous syndromes all present with variable degrees of psychomotor delay, congenital heart defects, facial dsymophism, short stature, skin abnormalities and a predisposition for malignancy. Dysregulation of the RAS-MAPKinase pathway is caused by germline mutations in genes involved in this pathway. Undoubtedly more genes causing related syndromes will be discovered in the near future since there are still a substantial number of genes in the pathway that are not yet associated with a known syndrome. And more mechanisms associated with RAS-MAPKinase signaling and the malignancy is an important challenge need to be clarify in the future.