arXiv subjects

Akram Yazdani

Publications and source records attributed to Akram Yazdani.

9 recordsLinked to original sources

arXiv2025

On-line learning of dynamic systems: sparse regression meets Kalman filtering

Learning governing equations from data is central to understanding the behavior of physical systems across diverse scientific disciplines, including physics, biology, and engineering. The Sindy algorithm has proven effective in leveraging sparsity to identify concise models of nonlinear dynamical systems. In this paper, we extend sparsity-driven approaches to real-time learning by integrating a cornerstone algorithm from control theory -- the Kalman filter (KF). The resulting Sindy Kalman Filter (SKF) unifies both frameworks by treating unknown system parameters as state variables, enabling real-time inference of complex, time-varying nonlinear models unattainable by either method alone. Furthermore, SKF enhances KF parameter identification strategies, particularly via look-ahead error, significantly simplifying the estimation of sparsity levels, variance parameters, and switching instants. We validate SKF on a chaotic Lorenz system with drifting or switching parameters and demonstrate its effectiveness in the real-time identification of a sparse nonlinear aircraft model built from real flight data.

cs.LG↗

arXiv2024

Metabolomic profiles in Jamaican children with and without autism spectrum disorder

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition with a wide range of behavioral and cognitive impairments. While genetic and environmental factors are known to contribute to its etiology, the underlying metabolic perturbations associated with ASD which can potentially connect genetic and environmental factors, remain poorly understood. Therefore, we conducted a metabolomic case-control study and performed a comprehensive analysis to identify significant alterations in metabolite profiles between children with ASD and typically developing (TD) controls. The objective of this study is to elucidate potential metabolomic signatures associated with ASD in children and identify specific metabolites that may serve as biomarkers for the disorder. We conducted metabolomic profiling on plasma samples from participants in the second phase of Epidemiological Research on Autism in Jamaica, a cohort of 200 children with ASD and 200 TD controls (2-8 years old). Using high-throughput liquid chromatography-mass spectrometry techniques, we performed a targeted metabolite analysis, encompassing amino acids, lipids, carbohydrates, and other key metabolic compounds. After quality control and imputation of missing values, we performed univariable and multivariable analysis using normalized metabolites while adjusting for covariates, age, sex, socioeconomic status, and child's parish of birth. Our findings revealed unique metabolic patterns in children with ASD for four metabolites compared to TD controls. Notably, three of these metabolites were fatty acids, including myristoleic acid, eicosatetraenoic acid, and octadecenoic acid. Additionally, the amino acid sarcosine exhibited a significant association with ASD. These findings highlight the role of metabolites in the etiology of ASD and suggest opportunities for the development of targeted interventions.

q-bio.BM↗

arXiv2019

Transcriptomic Causal Networks identified patterns of differential gene regulation in human brain from Schizophrenia cases versus controls

Common and complex traits are the consequence of the interaction and regulation of multiple genes simultaneously, which work in a coordinated way. However, the vast majority of studies focus on the differential expression of one individual gene at a time. Here, we aim to provide insight into the underlying relationships of the genes expressed in the human brain in cases with schizophrenia (SCZ) and controls. We introduced a novel approach to identify differential gene regulatory patterns and identify a set of essential genes in the brain tissue. Our method integrates genetic, transcriptomic, and Hi-C data and generates a transcriptomic-causal network. Employing this approach for analysis of RNA-seq data from CommonMind Consortium, we identified differential regulatory patterns for SCZ cases and control groups to unveil the mechanisms that control the transcription of the genes in the human brain. Our analysis identified modules with a high number of SCZ-associated genes as well as assessing the relationship of the hubs with their down-stream genes in both, cases and controls. In addition, the results identified essential genes for brain function and suggested new genes putatively related to SCZ.

q-bio.GN↗

arXiv2019

Insights into Complex Brain Functions Related to Schizophrenia Disorder through Causal Network Analysis

Gene expression represents a fundamental interface between genes and environment in the development and ongoing plasticity of the human organism. Individual differences in gene expression are likely to underpin much of human diversity, including psychiatric illness. Gene expression shows a distinct regulatory pattern in different tissues. Therefore, brain tissue analysis provides insights into brain disorder mechanisms. Furthermore, mechanistic understanding of gene regulatory pattern can be provided through studying the underlying relationships as a complex network. Identification of brain specific gene relationships provides a complementary framework in which to tackle the complex dysregulations that occur in neuropsychiatric and other neurological disorders. Using a systems approach established in Mendelian randomization and Bayesian Network, we integrated genetic and transcriptomic data from the common-mind consortium and identified transcriptomic causal networks in observational studies. Focusing on Schizophrenia disorder, we identified high impact genes and revealed their underlying pathways in brain tissue. In addition, we generated novel hypotheses including genes as causes of the schizophrenia-associated genes and new genes associated with Schizophrenia. This approach may facilitate a better understanding of the disease mechanism that is complementary to molecular experimental studies especially for complex systems and large-scale data sets.

q-bio.GN↗

arXiv2019

Using statistical techniques and replication samples for imputation of metabolite missing values

Background: Data preparation, such as missing values imputation and transformation, is the first step in any data analysis and requires crucial attention. Particularly, analysis of metabolites demands more preparation since those small compounds have recently been measurable in large scales with mass spectrometry techniques. We introduce novel statistical techniques for metabolite missing values imputation by utilizing replication samples. Results: To understand the nature of the missing values using replication samples, we obtained the empirical distribution of missing values and observed that the rate of missing values is approximately distributed as uniform across the metabolite range. Therefore, the missing values cannot be imputed with the lowest values. Using the identified distribution, we illustrated a simulation study to find an optimal imputation approach for metabolites. Conclusions: We demonstrated that the missing values in metabolomic data sets might not be necessarily low value. After identification of the nature of missing values, we validated K nearest neighborhood as an optimal approach for imputation.

q-bio.QM↗

arXiv2019

Genome analysis and pleiotropy assessment using causal networks with loss of function mutation and metabolomics

Background: Many genome-wide association studies have detected genomic regions associated with traits, yet understanding the functional causes of association often remains elusive. Utilizing systems approaches and focusing on intermediate molecular phenotypes might facilitate biologic understanding. Results: The availability of exome sequencing of two populations of African-Americans and European-Americans from the Atherosclerosis Risk in Communities study allowed us to investigate the effects of annotated loss-of-function (LoF) mutations on 122 serum metabolites. To assess the findings, we built metabolomic causal networks for each population separately and utilized structural equation modeling. We then validated our findings with a set of independent samples. By use of methods based on concepts of Mendelian randomization of genetic variants, we showed that some of the affected metabolites are risk predictors in the causal pathway of disease. For example, LoF mutations in the gene KIAA1755 were identified to elevate the levels of eicosapentaenoate (p-value=5E-14), an essential fatty acid clinically identified to increase essential hypertension. We showed that this gene is in the pathway to triglycerides, where both triglycerides and essential hypertension are risk factors of metabolomic disorder and heart attack. We also identified that the gene CLDN17, harboring loss-of-function mutations, had pleiotropic actions on metabolites from amino acid and lipid pathways. Conclusion: Using systems biology approaches for the analysis of metabolomics and genetic data, we integrated several biological processes, which lead to findings that may functionally connect genetic variants with complex diseases.

q-bio.GN↗

arXiv2018

A Multi-Trait Approach Identified Genetic Variants Including a Rare Mutation in RGS3 with Impact on Abnormalities of Cardiac Structure/Function

Heart failure is a major cause for premature death. Given heterogeneity of the heart failure syndrome, identifying genetic determinants of cardiac function and structure may provide greater insights into heart failure. Despite progress in understanding the genetic basis of heart failure through genome wide association studies, heritability of heart failure is not well understood. Gaining further insights into mechanisms that contribute to heart failure requires systematic approaches that go beyond single trait analysis. We integrated Bayesian multi-trait approach and Bayesian networks for the analysis of 10 correlated traits of cardiac structure and function measured for 3387 individuals with whole exome sequence data. While using single-trait based approaches did not find any significant genetic variant, applying the integrative Bayesian multi-trait approach, we identified 3 novel variants located in genes, RGS3, CHD3, and MRPL38 with significant impact on the cardiac traits such as left ventricular volume index, parasternal long axis interventricular septum thickness, and mean left ventricular wall thickness. Among these, the rare variant NC_000009.11:g.116346115C>A (rs144636307) in RGS3 showed pleiotropic effect on left ventricular mass index, left ventricular volume index and Maximum left atrial anterior-posterior diameter while RGS3 can inhibit TGF-beta signaling associated with left ventricle dilation and systolic dysfunction.

q-bio.GN↗

arXiv2018

Effect of Blast Exposure on Gene-Gene Interactions

Repeated exposure to low-level blast may initiate a range of adverse health problem such as traumatic brain injury (TBI). Although many studies successfully identified genes associated with TBI, yet the cellular mechanisms underpinning TBI are not fully elucidated. In this study, we investigated underlying relationship among genes through constructing transcript Bayesian networks using RNA-seq data. The data for pre- and post-blast transcripts, which were collected on 33 individuals in Army training program, combined with our system approach provide unique opportunity to investigate the effect of blast-wave exposure on gene-gene interactions. Digging into the networks, we identified four subnetworks related to immune system and inflammatory process that are disrupted due to the exposure. Among genes with relatively high fold change in their transcript expression level, ATP6V1G1, B2M, BCL2A1, PELI, S100A8, TRIM58 and ZNF654 showed major impact on the dysregulation of the gene-gene interactions. This study reveals how repeated exposures to traumatic conditions increase the level of fold change of transcript expression and hypothesizes new targets for further experimental studies.

q-bio.GN↗

arXiv2018

Integrated systems approach identifies pathways from the genome to triglycerides through a metabolomic causal network

Introduction: To leverage functionality and clinical relevance into understanding systems biology, one needs to understand the pathway of the genetic effects on risk factors/disease through intermediate molecular levels, such as metabolomics. Systems approaches integrate multi-omic information to find pathways to disease endpoints and make optimal inference decisions. Method: Here, we introduce a multi-stage approach to integrate causal networks in observational studies and GWAS to facilitate mechanistic understanding through identification of pathways from the genome to risk factors/disease via metabolomics. The pathways in causal networks reveal the underlying relationships behind observations, which do not play a significant role in more traditional correlative analyses, where one variable at a time is considered. Results: We identified a causal network over the metabolomic level using the genome directed acyclic graph (G-DAG), to systematically assess whether variations in the genome lead to variations in triglyceride levels as a risk factor of cardiovascular disease. We found LRRC46 and LRRC69 harboring loss-of-function mutations have significant effect on two metabolites with direct effects on triglyceride levels. We also found pathways of FAM198B and C6orf25 to triglycerides through indirect paths from metabolites. Conclusion: Integrating causal networks with GWAS facilitates mechanistic understanding in comparison to one-variable-at-a-time approaches due to accounting for relationships among components at intermediate molecular levels. This approach is complementary to experimental studies to identify efficacious targets in the age of big data sets.

q-bio.GN↗