SsPEP1, an Effector with Essential Cellular Functions in Sugarcane Smut Fungus

Biotrophic fungi have to infect their host to obtain nutrients and must establish an interaction with the host to complete their life cycle. In this process, effectors play important roles in manipulating the host’s immune system to avoid being attacked. Sporisorium scitamineum is the causative agent of sugarcane smut, the most important disease in sugarcane-producing regions worldwide. In this work, we functionally characterized the conserved effector PEP1 in S. scitamineum. The mating process and the expression of genes in the MAPK signaling pathway and the a and b loci were adversely affected in Sspep1-null mutants. The requirement for SsPEP1 in pathogenicity and symptom development was allele dosage-dependent, i.e., deleting one Sspep1 allele in the mating pair turned a normal black whip with abundant teliospores into a white whip with few teliospores; however, deleting both alleles almost abolished infectivity and whip development. ΔSspep1 mutants produced significantly less mycelium mass within infected plants. Additionally, SsPEP1 was identified as a potent inhibitor of sugarcane POD-1a peroxidase activity, implying that SsPEP1 may function to relieve reactive oxygen species-related stress within the host plant. Taken together, our work demonstrated that SsPEP1 is a multifaceted effector essential for S. scitamineum growth, development, and pathogenicity.

Positive correlation between transcriptomic stemness and PI3K/AKT/mTOR signaling scores in breast cancer, and a counterintuitive relationship with PIK3CA genotype

A PI3Kα-selective inhibitor has recently been approved for use in breast tumors harboring mutations in PIK3CA, the gene encoding p110α. Preclinical studies have suggested that the PI3K/AKT/mTOR signaling pathway influences stemness, a dedifferentiation-related cellular phenotype associated with aggressive cancer. However, to date, no direct evidence for such a correlation has been demonstrated in human tumors. In two independent human breast cancer cohorts, encompassing nearly 3,000 tumor samples, transcriptional footprint-based analysis uncovered a positive linear association between transcriptionally-inferred PI3K/AKT/mTOR signaling scores and stemness scores. Unexpectedly, stratification of tumors according to PIK3CA genotype revealed a “biphasic” relationship of mutant PIK3CA allele dosage with these scores. Relative to tumor samples without PIK3CA mutations, the presence of a single copy of a hotspot PIK3CA variant was associated with lower PI3K/AKT/mTOR signaling and stemness scores, whereas the presence of multiple copies of PIK3CA hotspot mutations correlated with higher PI3K/AKT/mTOR signaling and stemness scores. This observation was recapitulated in a human cell model of heterozygous and homozygous PIK3CAH1047R expression. Collectively, our analysis (1) provides evidence for a signaling strength-dependent PI3K-stemness relationship in human breast cancer; (2) supports evaluation of the potential benefit of patient stratification based on a combination of conventional PI3K pathway genetic information with transcriptomic indices of PI3K signaling activation.

Allele expression biases in mixed-ploid sugarcane accessions

Allele-specific expression (ASE) represents differences in the magnitude of expression between alleles of the same gene. This is not straightforward for polyploids, especially autopolyploids, as knowledge about the dose of each allele is required for accurate estimation of ASE. This is the case for the genomically complex Saccharum species, characterized by high levels of ploidy and aneuploidy. We used a Beta-Binomial model to test for allelic imbalance in Saccharum, with adaptations for mixed-ploid organisms. The hierarchical Beta-Binomial model was used to test if allele expression followed the expectation based on genomic allele dosage. The highest frequencies of ASE occurred in sugarcane hybrids, suggesting a possible influence of interspecific hybridization in these genotypes. For all accessions, ASEGs were less frequent than those with balanced allelic expression. These genes were related to a broad range of processes, mostly associated with general metabolism, organelles, responses to stress and responses to stimuli. In addition, the frequency of ASEGs in high-level functional terms was similar among the genotypes, with a few genes associated with more specific biological processes. We hypothesize that ASE in Saccharum is largely a genotype-specific phenomenon, as a large number of ASEGs were exclusive to individual accessions.

Biallelic TET2 mutation sensitizes to 5-azacitidine in acute myeloid leukemia

Precision medicine can significantly improve outcomes for cancer patients, but implementation requires comprehensive characterization of tumor cells to identify therapeutically exploitable vulnerabilities. Here we describe somatic biallelic TET2 mutation (focal deletion and nonsense mutation) in an elderly patient with acute myeloid leukemia (AML) that was chemoresistant to anthracycline and cytarabine, but acutely sensitive to 5-azacitidine (5-Aza) hypomethylating monotherapy, resulting in long-term morphological remission (overall survival (OS) 850 days). Given the role of TET2 as a regulator of genomic methylation, we hypothesized that mutant TET2 allele dosage affects response to 5-Aza. Using an isogenic cell model system and an orthotopic mouse xenograft, we demonstrate that biallelic TET2 mutations confer sensitivity to 5-Aza compared to cells with monoallelic mutation. We subsequently identified 29 additional patients from the Study Alliance Leukemia biobank with chromosome 4 abnormalities and identified two further patients with complex biallelic TET2 mutations, including one with trisomy 4, homozygosity across the long arm and an inactivating point mutation. We also screened patients recruited to the PETHEMA FLUGAZA phase 3 clinical trial and identified three patients with biallelic TET2 mutations, two of whom had responded very well to single agent 5-Aza (OS 767 and 579 days) despite having adverse risk AML and poor performance status. Our data argue in favor of using hypomethylating agents for chemoresistant disease or as first line therapy in patients with biallelic TET2-mutated AML and demonstrate the importance of considering mutant allele dosage in the implementation of precision medicine for cancer patients.

Cross-species amplification of microsatellites and identification of polyploid hybrids by allele dosage effects in Cobitis hankugensis × Iksookimia longicorpa hybrid complex (Actinopterygii: Cypriniformes: Cobitidae)

During the course of evolution, numerous taxa abandoned canonical sex and reproduced asexually. Examination of the Cobitis hankugensis × Iksookimia longicorpa asexual complex already revealed important evolutionary discoveries tackling phenomena like interspecific hybridization, non-Mendelian inheritance, polyploidy, and asexuality. Yet, as in other similar cases, the investigation is hampered by the lack of easily accessible molecular tools for efficient differentiation among genomotypes. Here, we tested the cross-species amplification of 23 microsatellite markers derived from distantly related species and investigated the extent to which such markers can facilitate the genome identification in the non-model hybrid complex. We found that 21 out of 23 microsatellite markers were amplified in all genomotypes. Five of them could be used for easy diagnostics of parental species and their hybrids due to species-specific amplification profiles. We also noted that three markers, i.e., IC654 and IC783 derived from Cobitis choii Kim et Son, 1984 and Iko_TTA01 from Iksookimia koreensis (Kim, 1975), had dosage-sensitive amplification efficiencies of species-specific alleles. This could be further used for reliable differentiation of genome composition in polyploids. The presently reported study introduces a noninvasive method applicable for the diagnosis of ploidy and genome composition of hybrids, which are not clearly distinguished morphologically. We showed that very detailed information may be obtained even from markers developed in distantly related taxa. Hybridization is being increasingly recognized as a driving force in evolution. Yet, proper detection of hybrids and their ploidy is particularly challenging, especially in non-model organisms. The present paper evaluates the power of microsatellite cross-amplification not only in the identification of hybrid forms but also in estimating their genome dosage on an example of a fish taxon that involves asexuality, hybridization as well as ploidy variation. It thus demonstrates the wide applicability of such cheap and non-invasive tools.

Coronary Artery Disease: Association Study of 5 Loci with Angiographic Indices of Disease Severity

Background. Different common gene variants were related to coronary artery disease (CAD) in many studies. Yet, the relation of these loci to the severity of CAD is not completely elucidated. Methods. We enrolled 520 subjects (315 CAD cases and 205 controls). CAD presence and extension were assessed by coronary angiography (CAG). Genotyping of five SNPs (namely, rs2230806 (1051G > A) in ABCA1 on chromosome 9, rs2075291 (553G > T) in ApoA5 on chromosome 11, rs320 in LPL on chromosome 8 intron (T → G at position 481), rs10757278 (c.22114477A > G), and rs2383206 (c.22115026 A > G) on chromosome 9p21 locus) was performed by allele-specific PCR. The degree and site of arterial lesions were used to classify patients, tested for association with CAD severity, and related to allele dosage. Results. The polymorphisms rs2383206 and rs10757278 showed significant associations with 2- and 3-vessel coronary disease (p =0.003 and 0.006, respectively). The homozygous GG genotypes of rs10757278 was associated with higher frequency of left anterior descending (LAD), right coronary artery (RCA) and left circumflex (LCX) diseases (p =0.002, 0.016 and 0.002, respectively). The GG genotypes of rs2383206 were found in higher percentage in patients with left main (LM) trunk and left circumflex (LCX) diseases ( p = 0.013 and 0.002, respectively). Conclusion. SNPs rs10757278 and rs2383206 allele dosage could predict CAD severity in the Saudi Arab population.

Genomic prediction with allele dosage information in highly polyploid species

Several studies have shown how to leverage allele dosage information to improve the accuracy of genomic selection models in autotetraploids. In this study we expanded the methodology used for genomic selection in autotetraploids to higher (and mixed) ploidy levels. We adapted the models to build covariance matrices of both additive and digenic dominance effects that are subsequently used in genomic selection models. We applied these models using estimates of ploidy and allele dosage to sugarcane and sweet potato datasets and validated our results by also applying the models in simulated data. For the simulated datasets, including allele dosage information led up to 140% higher mean predictive abilities in comparison to using diploidized markers. Including dominance effects was highly advantageous when using diploidized markers, leading to mean predictive abilities which were up to 115% higher in comparison to only including additive effects. When the frequency of heterozygous genotypes in the population was low, such as in the sugarcane and sweet potato datasets, there was little advantage in including allele dosage information in the models. Overall, we show that including allele dosage can improve genomic selection in highly polyploid species under higher frequency of different heterozygous genotypic classes and high dominance degree levels.