Mutations in KAL-1 gene of Kallmann Syndrome cases in NTU Hospital
|Keywords:||卡曼氏症候群;促性腺激素釋放激素;嗅覺喪失;原發性促性腺激素分泌不足的性腺發育低下症;Kallmann syndrome;gonadotropin releasing hormone;anosmia;idiopathic hypogonadotropic hypogonadism||Issue Date:||2009||Abstract:||
卡曼氏症候群（Kallmann syndrome）患者是一群屬原發性促性腺激素分泌不足的性腺發育低下症（idiopathic hypogonadotropic hypogonadism）且伴隨嗅覺低下（hyposmia）或嗅覺喪失（anosmia）的患者。這樣的患者由於下視丘不分泌「促性腺激素釋放激素」（GnRH），導致腦下垂體分泌黃體激素（LH）、濾泡刺激素（FSH）不足、或是LH與FSH雖分泌正常，但性腺對於這兩種激素卻毫無反應或是反應遲滯，以致性腺激素分泌不足，男性睪丸分泌的睪固酮素（testosterone），女性卵巢分泌女性激素雌二醇（estradiol）不足，而導致性發育遲滯。一般此症候群目前已知可分為四類型，KAL1是X染色體上KAL-1基因突變的類型，屬於X染色體性聯遺傳隱性模式；KAL2為FGFR1基因突變造成的，屬於體染色體顯性遺傳；另外還有KAL3（PROKR2基因）與KAL4（PROK2基因）共四類型。研究收集台大醫院內科與小兒內分泌專科門診歷年診斷為卡曼氏症候群的確診病患共八位，其中一位25歲女性（個案3）、其餘七位是年齡19到45歲不等的男性，包括一位5歲的男童。進行KAL-1基因14個exons的序列分析檢測，希望找出這些病患於KAL-1基因上功能性的突變。因序列分析檢測結果發現突變點的位置，多發生在exon 11（c.1600G>A）與exon 12（c.1833C>T），所造成的胺基酸改變為Val534Ile與synonymous mutation（Ile611），個案1、2、3、5、7、8均在此兩點突變，個案5除此兩突變點，還有exon 14上的四個突變點，c.1997A>T（Lys666Met）、c.2003G>A（Arg668His）、以及在3’端超過中止密碼的*19G>T與*21G>A。案6之5歲的男童，其突變則比較複雜，從exon 11（Intron 10交界處）一直到exon 14共有37個突變點位；顯然我們PCR反應所擴增的基因片段很可能並非其X染色體的exon11~14，而是Y染色體上Yq11.2上不再製造任何蛋白的pseudogene，KALP。案4則未找到任何突變的序列或點位。
Kallmann syndrome is a developmental disorder characterized by idiopathic hypothalamic hypogonadotropic hypogonadism with olfactory loss (anosmia or hyposmia：with low or poor sense of smell). These patients have delayed or absent puberty due to deficiency of hypothalamic gonadotropin-releasing hormone (GnRH), resulting in low secretion or absence of pituitary luteinizing hormone (LH), follicle-stimulating hormone (FSH). Even though the normal level of LH and FSH secretion may exist, there is no response or delayed response in sex hormone secretion from the gonads of these patients. These result in insufficient secretion of testosterone in male or ovarian secretion of estradiol in female. Currently this syndrome can be divided into four types, KAL1, caused by mutations in the KAL-1 gene located on X chromosome Xp22.3 and inherited in an X-linked recessive mode; KAL2, caused by mutations in FGFR; KAL3, caused by mutations in PROKR2 gene, and KAL4, caused by mutations in PROK2 genes. The KAL2 and KAL4 are inherited in an autosomal dominant mode except KAL3. n this study, we have collected a total number of eight patients with Kallmann syndrome in the clinics of Internal Medicine and the Pediatric Endocrine special clinic, in National Taiwan University Hospital. One was a 25-year-old female, and the other seven were males with their age range 19-45, and one 5-year-old boy. In this thesis, searching for mutations among these Kallmann syndrome patients were focused on the KAL-1 gene first. In order to delineate the functional mutations of KAL-1 genes among these patients, sequence analysis of all 14 exons in KAL-1 gene was performed. We found that two point mutations within the coding sequence (CDS) region in patients (subjects) 1, 2, 3, 5, 7, 8. These two mutations were in the exon 11 (c.1600G>A) and exon 12 (c.1833C>T), leading to the Val534Ile missense mutation and a synonymous mutation (Ile611). There were more mutations found in exon 14 of the Subject 5 in addition to the previous two point mutations. They were c.1997A>T (Lys666Met), c.2003G>A (Arg668His), *19G>T and *21G>A, and the latter two have been beyond the termination code in the 3 ''end. ubject 6 was a 5-year-old boy with a total of 37 mutations from exon 11 (at the junction between Intron 10 and exon 11) to the exon 14. It might arise from the possible incorrect amplification of the fragments from the pseudogene KALP which is homologue of KAL-1 on Y located in Yq11.2 by PCR reaction, instead of truly amplifying the real exon11-14 of KAL-1 on X chromosome.e did not find any mutations in the sequence of Subject 4 in KAL-1.
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