A parameter identification problem in stochastic homogenization

In porous media physics, calibrating model parameters through experiments is a challenge. This process is plagued with errors that come from modelling, measurement and computation of the macroscopic observables through random homogenization -- the forward problem -- as well as errors coming from the parameters fitting procedure -- the inverse problem. In this work, we address these issues by considering a least-square formulation to identify parameters of the microscopic model on the basis on macroscopic observables. In particular, we discuss the selection of the macroscopic observables which we need to know in order to uniquely determine these parameters. To gain a better intuition and explore the problem without a too high computational load, we mostly focus on the one-dimensional case. We show that the Newton algorithm can be efficiently used to robustly determine optimal parameters, even if some small statistical noise is present in the system

The "silver" Japanese quail and the MITF gene: causal mutation, associated traits and homology with the "blue" chicken plumage

<p>Abstract</p> <p>Background</p> <p>The <it>MITF </it>(<it>microphthalmia-associated transcription factor</it>) gene has been investigated in mice and various vertebrates but its variations and associated effects have not yet been explored much in birds. The present study describes the causal mutation <it>B </it>at the <it>MITF </it>gene responsible for the "silver" plumage colour in the Japanese quail (<it>Coturnix japonica</it>), and its associated effects on growth and body composition, and tests its allelism with the "blue" plumage colour mutation <it>Bl </it>in <it>Gallus gallus</it>.</p> <p>Results</p> <p>The semi dominant <it>B </it>mutation results from a premature stop codon caused by a 2 bp deletion in exon 11 of <it>MITF</it>. Homozygous "white" (<it>B/B</it>) quail which have a white plumage also show a slightly lower growth, lower body temperature, smaller heart, and lighter <it>pectoralis </it>muscles but more abdominal adipose tissue than the recessive homozygous "wild-type" (<it>+/+</it>) and heterozygous "silver" (<it>B/+</it>) quail. Similar observations on cardiac and body growth were made on mice (<it>Mus musculus</it>) homozygous for mutations at <it>MITF</it>. The production of chicken-quail hybrids with a white plumage obtained by crossing <it>Bl/+ </it>chicken heterozygous for the <it>blue </it>mutation with <it>B/B </it>white quail indicated that the mutations were allelic.</p> <p>Conclusion</p> <p>The "silver" Japanese quail is an interesting model for the comparative study of the effects of <it>MITF </it>in birds and mammals. Further investigation using a chicken family segregating for the "blue" plumage and molecular data will be needed to confirm if the "blue" plumage in chicken results from a mutation in <it>MITF</it>.</p

The quail genome:insights into social behaviour, seasonal biology and infectious disease response

Background: The Japanese quail (Coturnix japonica) is a popular domestic poultry species and an increasingly significant model species in avian developmental, behavioural and disease research. Results: We have produced a high-quality quail genome sequence, spanning 0.93 Gb assigned to 33 chromosomes. In terms of contiguity, assembly statistics, gene content and chromosomal organisation, the quail genome shows high similarity to the chicken genome. We demonstrate the utility of this genome through three diverse applications. First, we identify selection signatures and candidate genes associated with social behaviour in the quail genome, an important agricultural and domestication trait. Second, we investigate the effects and interaction of photoperiod and temperature on the transcriptome of the quail medial basal hypothalamus, revealing key mechanisms of photoperiodism. Finally, we investigate the response of quail to H5N1 influenza infection. In quail lung, many critical immune genes and pathways were downregulated after H5N1 infection, and this may be key to the susceptibility of quail to H5N1. Conclusions: We have produced a high-quality genome of the quail which will facilitate further studies into diverse research questions using the quail as a model avian species

Heterogeneity of genomic evolution and mutational profiles in multiple myeloma.

Multiple myeloma is an incurable plasma cell malignancy with a complex and incompletely understood molecular pathogenesis. Here we use whole-exome sequencing, copy-number profiling and cytogenetics to analyse 84 myeloma samples. Most cases have a complex subclonal structure and show clusters of subclonal variants, including subclonal driver mutations. Serial sampling reveals diverse patterns of clonal evolution, including linear evolution, differential clonal response and branching evolution. Diverse processes contribute to the mutational repertoire, including kataegis and somatic hypermutation, and their relative contribution changes over time. We find heterogeneity of mutational spectrum across samples, with few recurrent genes. We identify new candidate genes, including truncations of SP140, LTB, ROBO1 and clustered missense mutations in EGR1. The myeloma genome is heterogeneous across the cohort, and exhibits diversity in clonal admixture and in dynamics of evolution, which may impact prognostic stratification, therapeutic approaches and assessment of disease response to treatment

A polygenic risk score for multiple myeloma risk prediction

There is overwhelming epidemiologic evidence that the risk of multiple myeloma (MM) has a solid genetic background. Genome-wide association studies (GWAS) have identified 23 risk loci that contribute to the genetic susceptibility of MM, but have low individual penetrance. Combining the SNPs in a polygenic risk score (PRS) is a possible approach to improve their usefulness. Using 2361 MM cases and 1415 controls from the International Multiple Myeloma rESEarch (IMMEnSE) consortium, we computed a weighted and an unweighted PRS. We observed associations with MM risk with OR = 3.44, 95% CI 2.53–4.69, p = 3.55 × 10−15 for the highest vs. lowest quintile of the weighted score, and OR = 3.18, 95% CI 2.1 = 34–4.33, p = 1.62 × 10−13 for the highest vs. lowest quintile of the unweighted score. We found a convincing association of a PRS generated with 23 SNPs and risk of MM. Our work provides additional validation of previously discovered MM risk variants and of their combination into a PRS, which is a first step towards the use of genetics for risk stratification in the general population

The apobec mutational activity in multiple myeloma: from diagnosis to cell lines

Next generation sequencing (NGS) studies have highlighted the role of aberrant activity of APOBEC DNA deaminases in generating the mu- tational repertoire of multiple myeloma (MM). However, the contribu- tion of this mutational process across the landscape of plasma cell dyscrasias, or its prognostic role, has never been investigated in detail. To answer these unexplored aspects of MM biology, we used published NGS data from our own work as well as others, including the large CoMMpass trial for a total of 1153 whole-exomes of MM. Furthermore, we investigated 5 MGUS, 6 primary plasma cell leukemias (pPCL) and 18 MM cell lines (MMCL). Overall, we identified signatures of two mu- tational processes, one related to spontaneous deamination of methy- lated cytosines (30% of variants, range 0-100%) and one attributed to aberrant APOBEC activity (70% of variants, range 0-100%). APOBEC contribution was extremely heterogeneous among MM patients, but was correlated with a higher mutational burden (r=0.71, p=<0.0001) and with MAF gene translocations t(14;16) and t(14;20). The activity of APOBEC increased from MGUS to MM to pPCL, both in terms of ab- solute number of mutations and as percentage contribution. In MMCL we instead observed a bi-modal distribution whereby 8 cell lines showed the highest numbers of mutations caused by APOBEC (5/8 car- ried MAF translocations), while 10 where virtually devoid of APOBEC mutations (0/10 carried MAF translocations). The contribution of APOBEC to the total mutational repertoire in MM had a clear prognos- tic impact. MM patients with APOBEC mutations in the lowest quartile had a survival advantage over patients with APOBEC mutations in the highest quartile both in terms of progression-free survival (3-y PFS 46% vs 67% months, p=<0.0001) and overall survival (3-y OS 52% vs 83%, p=0.0084). This association was retained in a multivariate model that included age, gender, cytogenetic class, ISS, and quartiles of mutational load both in PFS [p=0.02, HR 2.06 (95IC 1.11-3.81] and OS [p=0.02, HR 2.88 (95IC 1.17-7.09)]. Interestingly we found that APOBEC mutations in the 4th quartile retained its independent prognostic respect to high mutational load and presence of MAF translocations. Overall, our data suggest that APOBEC-mediated mutagenesis is strongly involved in MM pathogenesis and its activity persists during different phases of evolution, playing a critical role in MM genomic complexity, and im- pacting prognosis of the patients