An Induced Mutation in HvRECQL4 Increases the Overall Recombination and Restores Fertility in a Barley HvMLH3 Mutant Background

Plant breeding relies on the meiotic recombination or crossing over to generate the new combinations of the alleles along and among the chromosomes. However, crossing over is constrained in the crops such as barley by a combination of the low frequency and biased distribution. In this study, we attempted to identify the genes that limit the recombination by performing a suppressor screen for the restoration of fertility to the semi-fertile barley mutant desynaptic10 (des10), carrying a mutation in the barley ortholog of MutL-Homolog 3 (HvMLH3), a member of the MutL-homolog (MLH) family of DNA mismatch repair genes. des10 mutants exhibit reduced recombination and fewer chiasmata, resulting in the loss of obligate crossovers (COs) leading to chromosome mis-segregation. We identified several candidate suppressor lines and confirmed their restored fertility in an Hvmlh3 background in the subsequent generations. We focus on one of the candidate suppressor lines, SuppLine2099, which showed the most complete restoration of fertility. We characterized this line by using a target-sequence enrichment and sequencing (TENSEQ) capture array representing barley orthologs of 46 meiotic genes. We found that SuppLine2099 contained a C/T change in the anti-CO gene RecQ-like helicase 4 (RECQL4) resulting in the substitution of a non-polar glycine to a polar aspartic acid (G700D) amino acid in the conserved helicase domain. Single nucleotide polymorphism (SNP) genotyping of F3 populations revealed a significant increase in the recombination frequency in lines with Hvrecql4 in the Hvmlh3 background that was associated with the restoration of fertility. The genotyping also indicated that there was nearly double the recombination levels in homozygous Hvrecql4 lines compared to the wild type (WT). However, we did not observe any significant change in the distribution of CO events. Our results confirm the anti-CO role of RECQL4 in a large genome cereal and establish the possibility of testing the utility of increasing recombination in the context of traditional crop improvement.

When to Consider Lynch Syndrome in Non-Colon and Non-Endometrial Malignancies

Lynch syndrome (LS) is a common genetic syndrome characterized by pathogenic mutations of DNA mismatch repair genes resulting in a hereditary predisposition to cancer. While typically associated with colonic and endometrial cancer, LS additionally influences the development of many other malignancies. The Amsterdam II and Revised Bethesda Guidelines are the established clinical criteria for diagnosing LS. These guidelines are based on the most general characteristics of LS and do not address specific characteristics of the less commonly LS-associated malignancies. For individuals that present initially with a non-colon and non-endometrial malignancy, recommendations and guidelines on when to consider screening for LS are limited. Therefore, it is essential that clinicians are familiar with distinct LS-associated patient- and tumor-specific characteristics, especially of the less common LS-associated cancers, so that LS’s diagnosis is not missed. In this review article, we focus on extra-colonic and extra-endometrial LS-associated cancers, paying particular attention to any established or currently investigated cancer features that help raise suspicion for LS and potentially lead to its earlier diagnosis. This review will also discuss current guidelines specific to each LS-associated malignancy.

Recent advances in Lynch syndrome

Lynch syndrome is one of the most common hereditary cancer syndromes and is characterized by the development of many cancers, such as colorectal cancer (CRC), endometrial cancer, ovarian cancer, stomach cancer and many other cancers. Lynch syndrome is caused by pathogenic germline variants in one of four DNA mismatch repair genes (MLH1, MSH2, MSH6, or PMS2) or by an EPCAM deletion. The MLH1 variant is correlated with the highest risk of CRC, while the MSH2 variant is correlated with the highest risk of other cancers. CRC is the most common cancer type that develops in individuals with Lynch syndrome, followed by endometrial cancer. Recent advances have been made to help us further understand the molecular pathogenesis of this disease and help improve diagnostic testing efficiency and surveillance strategies. Moreover, recent advances in immunotherapy provided by clinical trials also provide clinicians with more chances to better treat Lynch syndrome. This study aims to review many advances in the molecular genetics, clinical features, diagnosis, surveillance and treatment of Lynch syndrome.

Are there monogenic hereditary forms of bladder cancer or only genetic susceptibilities?

Bladder cancer (BC) is the most common cancer involving the urinary system and the ninth most common cancer worldwide. Tobacco smoking is the most important environmental risk factor of BC. Several single nucleotide polymorphisms have been validated by genome-wide association studies as genetic risk factors for BC. However, the identification of DNA mismatch-repair genes, including MSH2 in Lynch syndrome and MUTYH in MUTYH-associated polyposis, raises the possibility of monogenic hereditary forms of BC. Moreover, other genetic mutations may play a key role in familial and hereditary transmissions of BC. Therefore, the aim of this review is to focus on the major hereditary syndromes involved in the development of BC and to report BC genetic susceptibilities established with genome-wide significance level.

SAT-155 High Prevalence Alterations on DNA Mismatch Repair Genes Related to Lynch Syndrome in Pediatric Patients with Adrenocortical Tumor Carried of the Germline Mutation on TP53

Background: Adrenocortical cancer (ACC) is a rare malignant neoplasia associated with a variable clinical presentation. Pediatric patients generally have a better prognosis when compared to adults. In addition, unlike in adults where ACC which is usually sporadic, 50-80% of pediatric ACC is associated with genetic disorders such as Beckwith-Wiedemann and Li-Fraumeni syndromes. Recently, was showed that 3-5% of adult patients with ACC presented germline variants in DNA mismatch repair genes such as MSH2 and MSH6, the cause of Lynch syndrome (LS). The prevalence of these alterations in pediatric ACC is unknown. We aimed to investigate the prevalence of germline alterations in DNA mismatch repair genes among pediatric and adult patients with adrenocortical tumors (benign and malignant) carriers of the germline TP53 p.R337H mutation. Methods: 35 patients selected (30 pediatric and 5 adult) with functional tumors. ACC was diagnosed in 4 pediatric and in all adult patients. NGS was performed in 35 DNA blood samples by HNPCC MASTR Plus for the identification of SNV in 4 genes (MLH1, MSH2, MSH6, and PMS2) and 3’ UTR of EPCAM. Copy number variation (CNV) analyses were done by Copy Number Targeted Resequencing Analysis (CONTRA) and MLPA. The variants were classified, according to ACMG (American College Medical Genome) by Varsome platform. The protein expression was evaluated by Immunohistochemistry (IHC): MLH1 (clone ES05), MSH2 (FE11), MSH6 (EP49), and PMS2 (EP51). All patients were evaluated for variants in TP53. Results: NGS: 2 children presented 2 pathogenic allelic variants associated with LS (2/30, 6.6%), both patients with benign outcome and follow up of 4 years: 1 deletion in MLH1 (c.1500_1502del) and 1 nonsense in the MSH6 gene (c.328C>T p.Arg110X. CNV: MLPA specific for MLH1/MSH2 showed a normal copy number. ICH: the loss of expression in MLH1/PMS2 was identified in only one case without allelic variants. Discussion: Although our cohort is small, we observed 2 allelic pathogenic variants associated with LS among pediatric with adrenocortical tumors. It is higher than the prevalence of colorectal and endometrial cancer (3.2%) in LS. A personal and family history of LS tumors should be strongly considered for genetic risk assessment in pediatric patients with ACT. If the association with TP53 alteration can influence the tumor’s behavior with early clinical presentation, as seen in hereditary nonpolyposis colorectal cancer, it needs to be investigated. The patients with both alterations must be followed with surveillance, according to the US Multi-Society task force guideline for Lynch syndrome and for Li-Fraumeni syndrome.