Molecular Scanning On 5' Flanking Region Nt-839 To Nt-358 Of CACNA1S Gene In Patients With Thyrotoxic Periodic Paralysis Of Chinese

Objective: To explore whether mutation or polymorphism of 5' flankingregion nt -839 to nt -358 of CACNA1S gene exists in male ThyrotoxicPeriodic Paralysis (TPP) patients of Chinese by molecular scanning. Toexplore the distribution difference of the mutation or polymorphism amongTPP patients, Graves disease patients without periodic paralysis (GD),hypokalaemic periodic paralysis without hyperthyroidism (HPP withouthyperthyroidism, abbreviated as HPP) patients and normal controls (NC).Methods: Direct sequencing 5' flanking region nt -839 to nt -358 ofCACNA1S gene in 18 male TPP patients, 23 male HPP patients, 32 male GDpatients and 22 male normal controls.Results:1. One single nucleotide polymorphism (SNP) at the 5' flanking regionnucleotide (nt) -476 of CACNA1S gene were detected. The frequencies ofAA genotype in four groups were 50.0%, 52.17%, 50.0%, 68.2% while thefrequencies of AG genotype were 44.4%, 34.78%, 34.4%, 27.3%, and that ofGG genotype were 5.56%, 13.05%, 15.6%, 4.5%, respectively. No significantdifference in the SNP genotype distribution among TPP, HPP, GD and NCgroup was observed (Fisher's Exact Test P=0.744). No significant differencesin the thyroid hormone and TSH levels, plasma K⁺ and Ca²⁺ levels werefound among different SNP genotypes of TPP plus HPP group (P＞0.05).2. G/A mutation at nt -563 of CACNA1S gene were also detected. The frequencies of AG genotype in four groups were 0%, 26.09%, 9.37% and27.27%, respectively. The distribution of the two genotypes (GG and AG) atthis site showed statistical difference among the four groups (Fisher's ExactTest P=0.027), and the frequency of genotype AG in TPP was significantlylower than that in HPP (Fisher's Exact Test P=0.027) and NC (Fisher's ExactTest P=0.024). Significant difference in allele A or G distribution frequencyamong four groups was observed (Fisher's Exact Test P=0.037) and thefrequency of allele A in TPP was lower than that in HPP (Fisher's Exact TestP=0.032) and NC (Fisher's Exact Test P=0.030). No significant differences inthe thyroid hormone and TSH levels, plasma K⁺ and Ca²⁺ levels between thetwo genotypes of HPP patients were found.3. G/A mutation at nt -417, which had not been reported before, wasdetected in one HPP patient.4. The frequency of mutations at nt -476 plus nt -563 was analyzed, andit was significantly different from that of mutation at only one site or even nomutation group (Fisher's Exact Test P=0.047), the frequency of combinedmutations in TPP was lower than that in HPP (Fisher's Exact Test P=0.027),and the difference between TPP and NC group was not statisticallysignificant (Fisher's Exact Test P=0.053).Conclusion:1. There was no significant difference in the SNP genotype distributionat the 5' flanking region nt-476 of CACNA1S gene among TPP, HPP, GD andNC group, which was different from what had been reported.2. The frequencies of the AG genotype and allele A at the 5' flankingregion nt-563 of CACNA1S gene in TPP were significantly lower than HPPand NC group.3. The decrease of the frequency of the AG genotype or allele A atnt-563 may be related to thyrotoxic periodic paralysis in Chinese.