Intended purpose
The SALSA MLPA Probemix P241 MODY Mix 1 is an in vitro diagnostic (IVD)¹ or research use only (RUO) semi-quantitative assay² for the detection of deletions or duplications in the HNF4A, GCK, HNF1A, and HNF1B genes in order to confirm a potential cause for and clinical diagnosis of Maturity-Onset Diabetes of the Young (MODY) type 1, 2, 3, and 5, respectively, and for molecular genetic testing of at-risk family members. It is intended for use with genomic DNA isolated from human peripheral whole blood specimens.

Copy number variations (CNVs) detected with P241 MODY Mix 1 should be confirmed with a different technique. In particular, CNVs detected by only a single probe always require confirmation by another method. Most defects in the HNF4A, GCK and HNF1A genes, and some defects in the HNF1B gene are point mutations, none of which will be detected by MLPA. It is therefore recommended to use this assay in combination with sequence analysis.

Assay results are intended to be used in conjunction with other clinical and diagnostic findings, consistent with professional standards of practice, including confirmation by alternative methods, clinical genetic evaluation, and counselling, as appropriate. The results of this test should be interpreted by a clinical molecular geneticist or equivalent.

This device is not intended to be used for standalone diagnostic purposes, population screening, or for the detection of, or screening for, acquired or somatic genetic aberrations.

¹ Please note that this probemix is for in vitro diagnostic (IVD) use in the countries specified at the end of this product description. In all other countries, the product is for research use only (RUO).
² To be used in combination with a SALSA MLPA Reagent Kit and Coffalyser.Net analysis software

Clinical background
Maturity-onset diabetes of the young (MODY) is a group of inherited disorders of non-autoimmune diabetes mellitus which usually present in adolescence or young adulthood. MODY presents genetic, metabolic and clinical heterogeneity, however most cases share characteristics like β-cell dysfunction with an autosomal dominant inheritance and early-onset (typically <35 years) of hyperglycaemia that is not insulin-dependent at point of diagnosis. Other characteristics include extrapancreatic features and absence of pancreatic autoimmunity markers. MODY is thought to account for at least 1-3% of all diabetes. More information is available at https://www.ncbi.nlm.nih.gov/books/NBK500456/ and https://www.nature.com/articles/ejhg201414.

To date it has been proposed that pathogenic variants in at least 14 genes cause MODY. Each subtype is linked to a different gene. A portion of MODY may be caused by pathogenic variants in yet-to-be-identified genes or complex molecular alterations in the known MODY-related genes that were not detected by previous genetic testing methods. The four most common genetic causes of MODY are pathogenic variants in GCK (MODY 2) and HNF1A (MODY 3), each accounting for 30%-60% of all MODY, and HNF4A (MODY 1) and HNF1B (MODY 5 or renal cysts and diabetes (RCAD) syndrome), together accounting for about 10% of all MODY. MODY 5, also known as RCAD syndrome, is characterised by diabetes and nondiabetic renal disease resulting from abnormal renal development. Whole HNF1B gene deletions form a high proportion of RCAD cases. Other genes involved in MODY are listed in the table in the Product Description on page 2.

Probemix content
The SALSA MLPA Probemix P241-E1 MODY Mix 1 contains 52 MLPA probes with amplification products between 130 and 500 nucleotides (nt). This includes 12 probes for the HNF4A gene, 11 probes for the GCK gene, 11 probes for the HNF1A gene and 10 probes for the HNF1B gene. In addition, 8 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.mrcholland.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. More information on how to interpret observations on these control fragments can be found in the MLPA General Protocol and online at www.mrcholland.com.