RESUMO
Autosomal-dominant tubulo-interstitial kidney disease (ADTKD) encompasses a group of disorders characterized by renal tubular and interstitial abnormalities, leading to slow progressive loss of kidney function requiring dialysis and kidney transplantation. Mutations in UMOD, MUC1, and REN are responsible for many, but not all, cases of ADTKD. We report on two families with ADTKD and congenital anemia accompanied by either intrauterine growth retardation or neutropenia. Ultrasound and kidney biopsy revealed small dysplastic kidneys with cysts and tubular atrophy with secondary glomerular sclerosis, respectively. Exclusion of known ADTKD genes coupled with linkage analysis, whole-exome sequencing, and targeted re-sequencing identified heterozygous missense variants in SEC61A1-c.553A>G (p.Thr185Ala) and c.200T>G (p.Val67Gly)-both affecting functionally important and conserved residues in SEC61. Both transiently expressed SEC6A1A variants are delocalized to the Golgi, a finding confirmed in a renal biopsy from an affected individual. Suppression or CRISPR-mediated deletions of sec61al2 in zebrafish embryos induced convolution defects of the pronephric tubules but not the pronephric ducts, consistent with the tubular atrophy observed in the affected individuals. Human mRNA encoding either of the two pathogenic alleles failed to rescue this phenotype as opposed to a complete rescue by human wild-type mRNA. Taken together, these findings provide a mechanism by which mutations in SEC61A1 lead to an autosomal-dominant syndromic form of progressive chronic kidney disease. We highlight protein translocation defects across the endoplasmic reticulum membrane, the principal role of the SEC61 complex, as a contributory pathogenic mechanism for ADTKD.
Assuntos
Anemia/genética , Heterozigoto , Nefropatias/genética , Mutação , Canais de Translocação SEC/genética , Adulto , Idoso , Alelos , Sequência de Aminoácidos , Animais , Biópsia , Criança , Doença Crônica , Progressão da Doença , Retículo Endoplasmático/metabolismo , Exoma/genética , Feminino , Retardo do Crescimento Fetal/genética , Genes Dominantes , Complexo de Golgi/metabolismo , Humanos , Recém-Nascido , Nefropatias/patologia , Masculino , Pessoa de Meia-Idade , Modelos Moleculares , Mutação de Sentido Incorreto/genética , Neutropenia/genética , Linhagem , Fenótipo , RNA Mensageiro/análise , RNA Mensageiro/genética , Canais de Translocação SEC/química , Síndrome , Adulto Jovem , Peixe-Zebra/embriologia , Peixe-Zebra/genéticaRESUMO
PURPOSE OF REVIEW: Thoracic aortic aneurysm (TAA) dissection is an important cause of death in the western world. Especially in young adults, the genetic contribution to this disease is estimated to be high, as at least one out of five probands has a positive family history for aortic aneurysms/dissections. In recent years, major progress has been made in the identification of several genes underlying both syndromic and nonsyndromic forms of TAA. RECENT FINDINGS: This review will focus on the current knowledge of a recently discovered syndromic form of TAA, namely the Loeys-Dietz syndrome or LDS. SUMMARY: LDS is caused by mutation in the genes encoding the transforming growth factor beta receptor 1 and 2 (TGFBR1 and TGFRB2) and is characterized by aggressive aortic/arterial disease. The clinical characteristics, molecular findings and pathophysiological mechanisms are summarized. The discovery of this entity has confirmed a key role for transforming growth factor beta signaling in aortic aneurysmal disease. Study of the natural history of this condition has revealed important lessons. The arterial disease is widespread and can involve all aortic segments and major branching arteries, necessitating cardiovascular imaging beyond the aortic root segment. Moreover, dissections occur at smaller diameters than in Marfan syndrome, leading to earlier surgery at smaller aortic diameters. Current surgical experience with LDS is excellent, offering a good long-term prognosis with timely identification of the disease.