Cottrell Emily, Maharaj Avinaash, Williams Jack, Chatterjee Sumana, Cirillo Grazia, Miraglia Del Giudice Emanuele, Festa Adalgisa, Palumbo Stefania, Capalbo Donatella, Salerno Mariacarolina, Pignata Claudio, Savage Martin O, Schilbach Katharina, Bidlingmaier Martin, Hwa Vivian, Metherell Louise A, Grandone Anna, Storr Helen L
Centre for Endocrinology, William Harvey Research Institute: Barts and The London School of Medicine and Dentistry William Harvey Research Institute.
Studies of Campania Luigi Vanvitelli, Department of Woman, Child, General and Specialized Surgery.
J Clin Endocrinol Metab. 2021 Jul 28;107(1):e401-16. doi: 10.1210/clinem/dgab550.
Severe forms of Growth Hormone Insensitivity (GHI) are characterized by extreme short stature, dysmorphism and metabolic anomalies.
Identification of the genetic cause of growth failure in 3 'classical' GHI subjects.
A novel intronic GHR variant was identified, and in vitro splicing assays confirmed aberrant splicing. A 6Ω pseudoexon GHR vector and patient fibroblast analysis assessed the consequences of the novel pseudoexon inclusion and the impact on GHR function.
We identified a novel homozygous intronic GHR variant (g.5:42700940T>G, c.618 + 836T> G), 44bp downstream of the previously recognized intronic 6Ψ GHR pseudoexon mutation in the index patient. Two siblings also harbored the novel intronic 6Ω pseudoexon GHR variant in compound heterozygosity with the known GHR c.181C>T (R43X) mutation. In vitro splicing analysis confirmed inclusion of a 151bp mutant 6Ω pseudoexon not identified in wild-type constructs. Inclusion of the 6Ω pseudoexon causes a frameshift resulting in a non-functional truncated GHR lacking the transmembrane and intracellular domains. The truncated 6Ω pseudoexon protein demonstrated extracellular accumulation and diminished activation of STAT5B signaling following growth hormone stimulation.
Novel GHR 6Ω pseudoexon inclusion results in loss of GHR function consistent with a severe GHI phenotype. This represents a novel mechanism of Laron syndrome and is the first deep intronic variant identified causing severe postnatal growth failure. The 2 kindreds originate from the same town in Campania, Southern Italy, implying common ancestry. Our findings highlight the importance of studying variation in deep intronic regions as a cause of monogenic disorders.
严重型生长激素不敏感症（GHI）的特征为身材极度矮小、畸形和代谢异常。
确定3名“典型”GHI患者生长发育迟缓的遗传原因。
鉴定出一种新的内含子GHR变异体，体外剪接试验证实剪接异常。采用一个6Ω假外显子GHR载体和患者成纤维细胞分析，评估新的假外显子插入的后果及其对GHR功能的影响。
我们在索引患者中鉴定出一种新的纯合内含子GHR变异体（g.5:42700940T>G，c.618 + 836T>G），位于先前识别的内含子6Ψ GHR假外显子突变下游44bp处。两名同胞也携带这种新的内含子6Ω假外显子GHR变异体，与已知的GHR c.181C>T（R43X）突变呈复合杂合状态。体外剪接分析证实野生型构建体中未发现的一个151bp突变型6Ω假外显子被插入。6Ω假外显子的插入导致移码，产生一种无功能的截短型GHR，缺失跨膜和细胞内结构域。截短的6Ω假外显子蛋白表现为细胞外积聚，生长激素刺激后STAT5B信号激活减弱。
新的GHR 6Ω假外显子插入导致GHR功能丧失，与严重的GHI表型一致。这代表了拉伦综合征的一种新机制，是首个被鉴定出导致严重出生后生长发育迟缓的深度内含子变异体。这两个家族来自意大利南部坎帕尼亚的同一个城镇，提示有共同的祖先。我们的研究结果强调了研究深度内含子区域变异作为单基因疾病病因的重要性。
