Novel chymotrypsin C (CTRC) variants from real-world genetic testing of pediatric chronic pancreatitis cases.
Pancreatology
; 24(5): 690-697, 2024 Aug.
Article
em En
| MEDLINE
| ID: mdl-38876922
ABSTRACT
BACKGROUND:
Chymotrypsin C (CTRC) protects the pancreas against unwanted intrapancreatic trypsin activity through degradation of trypsinogen. Loss-of-function CTRC variants increase the risk for chronic pancreatitis (CP). The aim of the present study was to characterize novel CTRC variants found during genetic testing of CP cases at a pediatric pancreatitis center.METHODS:
We used next-generation sequencing to screen patients. We analyzed the functional effects of CTRC variants in HEK 293T cells and using purified enzymes.RESULTS:
In 5 separate cases, we detected 5 novel heterozygous CTRC variants c.407C>T (p.Thr136Ile), c.550G>A (p.Ala184Thr), c.627Cdup (p.Ser210Leufs∗?, where the naming indicates a frame shift with no stop codon), c.628T>C (p.Ser210Pro), and c.779A>G (p.Asp260Gly). Functional studies revealed that with the exception of p.Ser210Leufs∗?, the CTRC variants were secreted normally from transfected cells. Enzyme activity of purified variants p.Thr136Ile, p.Ala184Thr, and p.Asp260Gly was similar to that of wild-type CTRC, whereas variant p.Ser210Pro was inactive. The frame-shift variant p.Ser210Leufs∗? was not secreted but accumulated intracellularly, and induced endoplasmic reticulum stress, as judged by elevated mRNA levels of HSPA5 and DDIT3, and increased mRNA splicing of XBP1.CONCLUSIONS:
CTRC variants p.Ser210Pro and p.Ser210Leufs∗? abolish CTRC function and should be classified as pathogenic. Mechanistically, variant p.Ser210Pro directly affects the amino acid at the bottom of the substrate-binding pocket while the frame-shift variant promotes misfolding and thereby blocks enzyme secretion. Importantly, 3 of the 5 novel CTRC variants proved to be benign, indicating that functional analysis is indispensable for reliable determination of pathogenicity and the correct interpretation of genetic test results.Palavras-chave
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Base de dados:
MEDLINE
Assunto principal:
Quimotripsina
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Testes Genéticos
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Pancreatite Crônica
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Chaperona BiP do Retículo Endoplasmático
Limite:
Adolescent
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Child
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Female
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Humans
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Male
Idioma:
En
Ano de publicação:
2024
Tipo de documento:
Article