2型3色覚と診断された女性先天赤緑色覚異常者に対する遺伝子診断の試み

Molecular genetic analysis of a woman with red-green color vision deficiency diagnosed with deuteranomalous trichromacy

要約　目的：2型3色覚と診断された女性に対し遺伝子診断を試みた。方法：22歳女性（発端者）とその両親に対し，アノマロスコープによる診断とパネルD-15による程度判定を行った。X染色体上のL・M視物質遺伝子配列をPCR（polymerase chain reaction）法で決定し，上流の2つの遺伝子から想定される視物質の分光吸収極大波長の差を波長差として求めた。結果：発端者と父親は2型3色覚（軽度異常）と診断され，母親は正常色覚で保因者と考えられた。発端者は2種類の異なったM-Lハイブリッド遺伝子を有し，それぞれのX染色体上遺伝子配列における波長差は4nmと8nmであった。結論：2型3色覚女性の遺伝子型は，両親の色覚検査と遺伝子解析によって決定できる場合がある。

Abstract.　Purpose：To perform molecular genetic analysis of a woman with X-linked red-green color vision deficiency diagnosed with deuteranomalous trichromacy. Subjects and Methods：A 22-year-old woman（proband）and her parents were included in this study. Diagnosis of red-green color vision defect was made with a Nagel Type Ⅰ anomaloscope. Severity of color vision defect was determined by the Farnsworth Panel D-15 test. Genotypes of L and M visual pigment genes were determined by polymerase chain reaction. Difference in the peaks of the absorbance（λmax）between the first two visual pigment genes was calculated. Results：The proband and her father were diagnosed with deuteranomalous trichromacy（mild form）. Her mother was an obligate carrier of deuteranomaly because the mother's color vision was normal. Molecular genetic analysis showed the proband to have two distinct M-L hybrid genes. The first two expressed pigments from each X-chromosome gene array differed in λmax by 4 nm and 8 nm respectively. Conclusion：Above findings show that it is possible to determine genotype of a female proband with deuteranomaly when both genetic and color vision testing are performed in other family members of the proband.