Candidate Gene Mapped Of X-linked Recessive Growth Hormone Deficiency In A Chinese Family

BackgroundShort stature refers to a height of children which is below expected and usually defined as height more than2standard deviation (2SD) or in the following3rd percentage below for age and sex and race. Growth hormone deficiency (GHD) is the clinical common disease, its incidence is about1/5000～1/4000. If the disease can't be timely diagno sized and treated, it will lead to a significant short, adult incidence of cardiovascular disease increases. With growth hormone deficiency,there are some other pituitary hormone deficiency such as central hypothyroidism,adrenal cortical hormone (ACTH) deficiency and gonadal dysgenesis. GHD mostly is sporadic occurrence, and some is autosomal recessive or dominant genetic disease. According to the different genetic model, it can be divided into3types:IGHD type Ⅰ is an autosomal recessive genetic, IGHD type Ⅱ is an autosomal dominant and IGHD type Ⅲ is an x-linked recessive inheritance.Aim To map candidate genes of the growth hormone deficiency in a Chinese family by family investigation and molecular biology technologies.Subjects and Methods1.Investigation and clinical treatment of the family:Three generations of a family were investigated and serum growth hormone of the patients with short stature were detected by the insulin tolerance and arginine stimulation tests.Related clinical data such as TSH,ACTH,bone age and pituitary MRI were collected.2. SOX3gene sequencing:The DNA of16family members was extracted, primers of SOX3exon were designed and SOX3gene was sequenced after PCR program. Then the SOX3gene exon copy number variation were detected in the proband family.3. Polymorphic microsatellite DNA markers mapping study:Genomic DNA of18family members was extracted,19STR markers and linkage analysis were done by MERLIN software.4. The whole human genome exon sequencing and candidate gene validation:application of whole genome exon sequencing of three members of the family(the proband and his mother's brothers,one with GHD and the other with normal.) and combined with bioinformatics analysis to find the family special SNP and find the candidate genes which were sequenced in the family.Results1. Family investigation and clinical treatment:1.1In the family,there are only the male has GHD;1.2There are only the sons have GHD,however, the parents and the sisters do not have the disease, showing the son's pathogenic gene inherited from his mother;1.3The brother of patients,his mother's brother and sons of his mother's sisters are sick. Accordingly, it is confirmed to be a X linked recessive heredity.1.4The height rate of three patients with GHD was improved significantly after recombinant human growth hormone therapy and their adult heights will be improved.2. The SOX3gene including500bp of the promoter was sequenced and no mutation was found in the all members. The copy number variation of SOX3gene was detected in the proband family, his mother's CNV expression of SOX3gene was twice than the male which means that the CNV of SOX3was normal.3. By19STR markers and linkage analysis, we found that the disease gene localized on the STR markers DXS987and DXS1226(LOD score=2.408,θ=0).4. The whole genome exon sequencing and verification in the family found that EGFL6gene (c.1603G>A; p.Asp535Asn) and FTHL17gene(c.442G>T, c.443A>T; p.Glu148Leu) were homozygous mutations in the male patients and heterozygous mutations in the obligate female carriers, while the other normal male were wildtype homozygous. Conclusion This study confirms a new X-linked recessive inherited disease in a Chinese family with growth hormone deficiency and the candidate gene is mapped to Xp22.3-Xp11. EGFL6and FTHL17gene maybe a candidate gene.This research is to find the key pathogenic candidate gene regions and found that EGFL6,FTHL17may be the candidate gene of growth hormone deficiency in this family. It is the first report about genetic researchs of X-linked recessive growth hormone deficiency in our country. To our best knowledge, it is the first report about Xp22.3-Xpl1regions with x-linked recessive growth hormone deficiency in the world. It is important to contribute to the etiology and diagnosis of growth hormone deficiency. In the future, the candidate gene function of Xp22.3-Xp11regions with GHD will be done and make an important contribution to the genetic diagnosis,genetic screening of GHD.