The SALSA MLPA Probemix P242 Pancreatitis is a research use only (RUO)
assay for the detection of deletions or duplications in the PRSS1, SPINK1 and CTRC genes, which are associated with Hereditary Pancreatitis.
Hereditary Pancreatitis (HP; OMIM # 167800) is characterised by recurrent episodes of inflammation of the pancreas that progresses to chronic pancreatitis. HP has an autosomal dominant pattern of inheritance, and is defined by two or more individuals with pancreatitis in two or more generations of a family, or pancreatitis associated with a known germline pathogenic variant.
PRSS1 encodes trypsin-1 (cationic trypsinogen), a major pancreatic digestive serine peptidase enzyme, which is produced and secreted by the pancreas. PRSS1 pathogenic variants typically result in a trypsin protein that is either prematurely activated, while it is still in the pancreas, or resistant to degradation. Duplication of PRSS1, leading to an increase of the protein, also causes HP. Furthermore, gene conversion between PRSS1 and PRSS2 has been reported (Nemeth and Sahin-Toth 2014, Rygiel et al. 2015). In 90% of the cases, hereditary pancreatitis is caused by two point mutations in the PRSS1 gene, R122H (~65%) and N29I (25%) (Nemeth and Sahin-Toth 2014). Gene conversion between PRSS1 and PRSS2 exon 2 and the subsequent intron can occur, resulting in the N29I mutation together with N54S, a non-pathogenic mutation (Teich et al. 2005). In less than 6% of the cases, HP is caused by PRSS1 (large) deletions/duplications.
SPINK1 encodes the serine protease inhibitor Kazel-type 1. Pathogenic variants in SPINK1 can lead to autosomal recessive pancreatitis, and have been identified in approximately 20% of families with hereditary pancreatitis, without a PRSS1 germline pathogenic variant. The risk for developing acute pancreatitis is highly increased when the N34S mutation in SPINK1 is present (Koziel et al. 2015).
CTRC encodes chymotrypsin C (CTRC), a low-abundance pancreatic digestive enzyme that is synthetized with PRSS1. CTRC is important for the degradation of the prematurely activated trypsin within the pancreas. Pathogenic variants of CTRC have been associated with chronic pancreatitis (Masson et al. 2008).
While identification of a heterozygous PRSS1 pathogenic variant confirms a diagnosis of hereditary pancreatitis, the presence of isolated pathogenic variants in the SPINK1 or CTRC genes is insufficient to cause pancreatitis (Masson et al. 2013).
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The SALSA MLPA Probemix P242-C1 Pancreatitis contains 32 MLPA probes with amplification products between 136 and 436 nucleotides (nt). This includes six probes for the PRSS1 gene, including 2 probes for exon 1. Furthermore, it contains one upstream and two downstream probes on 7q34. Five probes are included for the SPINK1 gene, detecting exons 2, 3, 4, 5 and a region upstream of exon 1. Eight probes are included detecting all exons of CTRC gene. In addition, ten reference probes are included that detect autosomal chromosomal locations. Complete probe sequences and the identity of the genes detected by the reference probes are available online (www.mlpa.com).
This probemix contains nine quality control fragments generating amplification products between 64 and 105 nt: four DNA Quantity fragments (Q-fragments), two DNA Denaturation fragments (D-fragments), one Benchmark fragment, and one chromosome X and one chromosome Y-specific fragment (see table below). More information on how to interpret observations on these control fragments can be found in the MLPA General Protocol and online at www.mlpa.com