Vitamin D-dependent rickets type 1A (VDDR1A) is a rare autosomal recessively inherited disorder due to loss-of-function mutations in the CYP27B1 gene. CYP27B1 encodes an enzyme of 25-hydroxyvitamin D-1α-hydroxylase for converting inactive 25-OHD to biologically active 1,25-(OH)₂D.

To identify underlying genetic defects in patients with VDDR1A.

Twelve patients from 7 Turkish and 2 Saudi families were investigated. The coding exons and intron-exon boundaries of the CYP27B1 gene were amplified by Polymerase Chain Reaction (PCR) from peripheral lymphocyte DNA. PCR products were directly sequenced. The consequences of c.590G > A mutation were analyzed by in silico and functional analysis.

CYP27B1 mutations were identified in all the patients. Two novel mutations were identified in two separate families: c.171delG (family 7) and c.398_400dupAAT (family 8). The intra-exon deletion of c.171delG resulted in a frameshift and premature stop codon 20 amino acids downstream from the mutation (p.L58Cfs^∗20). The intra-exon duplication of c.398_400dupAAT generated a premature stop codon at the mutation site (p.W134^∗). A missense c.590G > A (p.G197D) mutation was found in a patient from family 4 and caused a defect in pre-mRNA splicing. As a result, two populations of transcripts were detected: the majority of them with intron 3 retention (83%), and the minority (17%) being properly spliced transcripts with about 16% of wild-type enzymatic activity. The remaining nine patients from six families carried a previously reported c.1319_1325dupCCCACCC (F443Pfs^∗24) mutation. Clinically, all the patients need continued calcitriol treatment, which was consistent with inactivation of 25-hydroxy vitamin D1α-hydroxylase activity.

Two novel frameshift CYP27B1 mutations were identified and predicted to inactivate 25-hydroxyvitamin D-1α-hydroxylase. The loss of enzymatic activity by c.590G > A missense mutation was mainly caused by aberrant pre-mRNA splicing.

维生素 D 依赖性佝偻病 1A 型 (VDDR1A) 是一种罕见的常染色体隐性遗传疾病，由于CYP27B1基因。CYP27B1编码一种 25-羟基维生素 D-1α-羟化酶，用于将无活性的 25-OHD 转化为具有生物活性的 1,25-(OH) ₂ D。

识别 VDDR1A 患者潜在的遗传缺陷。

对来自 7 个土耳其家庭和 2 个沙特家庭的 12 名患者进行了调查。编码外显子和内含子-外显子边界CYP27B1通过聚合酶链式反应 (PCR) 从外周淋巴细胞 DNA 中扩增基因。PCR产物直接测序。c.590G > A 突变的后果分析如下：计算机和功能分析。

CYP27B1在所有患者中都发现了突变。在两个不同的家族中发现了两个新的突变：c.171delG（家族 7）和 c.398_400dupAAT（家族 8）。c.171delG 的外显子内缺失导致突变下游 20 个氨基酸的移码和过早终止密码子 (p.L58Cfs ^* 20)。c.398_400dupAAT 的外显子内重复在突变位点产生了一个过早的终止密码子 (p.W134 ^*）。在来自 4 家族的患者中发现了错义 c.590G > A (p.G197D) 突变，并导致前 mRNA 剪接缺陷。结果，检测到两个转录物群：它们中的大多数具有内含子 3 保留 (83%)，少数 (17%) 是具有约 16% 的野生型酶活性的正确剪接转录物。来自六个家庭的其余九名患者携带先前报道的 c.1319_1325dupCCCACCC (F443Pfs ^* 24) 突变。临床上，所有患者均需继续骨化三醇治疗，这与 25-羟基维生素 D1α-羟化酶活性失活一致。

两种新颖的移码器CYP27B1突变被鉴定并预测使25-羟基维生素D-1α-羟化酶失活。c.590G > A错义突变导致酶活性丧失主要是由异常的pre-mRNA剪接引起的。