RESUMO
Generalized lipodystrophy is a feature of various hereditary disorders, often leading to a progeroid appearance. In the present study we identified a missense and a frameshift variant in a compound heterozygous state in SUPT7L in a boy with intrauterine growth retardation, generalized lipodystrophy, and additional progeroid features. SUPT7L encodes a component of the transcriptional coactivator complex STAGA. By transcriptome sequencing, we showed the predicted missense variant to cause aberrant splicing, leading to exon truncation and thereby to a complete absence of SUPT7L in dermal fibroblasts. In addition, we found altered expression of genes encoding DNA repair pathway components. This pathway was further investigated and an increased rate of DNA damage was detected in proband-derived fibroblasts and genome-edited HeLa cells. Finally, we performed transient overexpression of wildtype SUPT7L in both cellular systems, which normalizes the number of DNA damage events. Our findings suggest SUPT7L as a novel disease gene and underline the link between genome instability and progeroid phenotypes.
Assuntos
Retardo do Crescimento Fetal , Lipodistrofia Generalizada Congênita , Fatores de Transcrição , Humanos , Masculino , Dano ao DNA , Reparo do DNA/genética , Retardo do Crescimento Fetal/genética , Fibroblastos/metabolismo , Células HeLa , Lipodistrofia/genética , Lipodistrofia Generalizada Congênita/genética , Mutação com Perda de Função , Mutação de Sentido Incorreto , Fatores de Transcrição/genéticaRESUMO
Insertions are rare chromosomal rearrangements resulting from a three breaks mechanism. The risk of chromosomal imbalance in the offspring is estimated to be 15-50%. We have identified a familial history of direct, paracentric intrachromosomal 9q insertion, balanced in healthy members. For intrachromosomal insertions, unbalanced products in the offspring are always recombinants and in our case, reciprocal deletion and duplication of the inserted segment (9q22.31-9q31.1) were observed. These imbalances involved several genes, including PTCH1. PTCH1 haploinsufficiency causes Gorlin syndrome, an autosomal dominant disorder usually linked to the gene mutation but sometimes due to a 9q deletion. Clinical findings are different in 9q deletions and duplications including PTCH1, notably concerning the predisposition to benign and malignant tumors reported in the Gorlin syndrome. Furthermore, some features may be reciprocal. This history of intrachromosomal insertion highlights the importance of morphological cytogenetic analyses to provide an accurate genetic counseling.
Assuntos
Anormalidades Múltiplas/diagnóstico , Cromossomos Humanos Par 9/genética , Deficiências do Desenvolvimento/diagnóstico , Receptores de Superfície Celular/genética , Anormalidades Múltiplas/genética , Adulto , Deleção Cromossômica , Hibridização Genômica Comparativa , Deficiências do Desenvolvimento/genética , Feminino , Humanos , Lactente , Masculino , Mutagênese Insercional , Receptores Patched , Receptor Patched-1 , LinhagemRESUMO
Chromosomal rearrangements involving the MLL gene at band 11q23 are the most common genetic alteration encountered in infant acute myeloid leukemia. Reciprocal translocation represents the most frequent form of MLL rearrangement. Currently, more than 60 partner genes have been identified. We report here a case of de novo acute myeloid leukemia with a t(11;22)(q23;q11) in a 23-month-old child. Fluorescence in situ hybridization study revealed that the 3'MLL segment was translocated onto the derivative chromosome 22 and the breakpoint on chromosome 22 was located in or near the SEPT5 gene at 22q11.21. Long distance inverse-polymerase chain reaction was used to identify precisely the MLL partner gene and confirmed the MLL-SEPT5 fusion transcript. Involvement of the SEPT5 gene in MLL rearrangement occurs very rarely. Clinical, cytogenetic and molecular features of acute myeloid leukemia with a MLL-SEPT5 fusion gene are reviewed.