全面分析親代基因組對小鼠大腦的影響

Abstract

基因組印記是後代基因表達中受特定親代來源影響的現象。基因組印記的衝突理論指出，具有母系偏好的基因表達會促進出生體重的降低、成體大腦的縮小，以及較具有同情心和不自戀的性格，從而對母親的需求減少。在具有父系偏好的基因表達中將發生相反的情況。為了進一步探討親代基因組對後代行為產生的影響，我們想了解在分子、行為和電生理的層次上，親代基因組對其後代的影響。為此我們使用了兩個不同的小鼠品系：CAST / EiJ和C57BL / 6以及它們的正向（F1i）和反向（F1r）雜交的F1雜種。在行為方面，我們進行了學習、記憶，以及與焦慮和壓力相關的測試，以評估整體心理健康狀況。我們還進行了數種感覺與運動測試，以評估小鼠的整體身體健康狀況。我們在行為測試中觀察到雜種小鼠的異質遺傳，並在睡眠-覺醒模式、社交、焦慮和壓力反應中觀察到不同的遺傳模式。兒茶酚胺去甲腎上腺素（NE）有助於調節上述行為。 因此，我們檢查了不同大腦區域中兒茶酚胺合成中的限速酶酪氨酸氫氧化物（TH）的水平，發現四隻小鼠腦幹中TH的差異表達。 由於位於腦幹的藍斑軌跡（LC）是大腦NE的主要生產中心，因此我們決定研究小鼠LC神經元電特性的差異，這可能會導致雜種小鼠的行為差異。 我們觀察到雜種小鼠的放電特性與其親本菌株不同，這可能是影響小鼠之間行為差異的因素。B6、CAST、F1i和F1r小鼠全腦的RNA定序分析和GO分析證實了我們觀察到的某些行為。此外，我們進行了雜交小鼠大腦皮層的興奮神經元和星形膠質細胞的RNA定序分析。我們使用生物資訊學工具分析數據，製作了特定細胞類型中潛在印跡基因的列表，並確定了四個新的細胞類型特異性印跡基因。我們的跨學科工作使我們能夠欣賞雜種基因組的複雜性以及親代基因組對後代表現型的貢獻

Genomic imprinting is the phenomenon of a parent of origin-specific influence in the gene expression of the offspring. The conflict theory of genomic imprinting states that a maternal bias in gene expression promotes lower birth weight, smaller adult brain and an empathizing and less narcissistic personality causing fewer demands on the mother. The opposite would occur for gene expression with a paternal bias. To explore this theme of parental genome affecting offspring behavior further, we wanted to look at the molecular, behavior, and electrophysiological level of effects of parental genomes on their offsprings. To do this, we used two distinct mouse sub-strains: CAST/EiJ and C57BL/6 and the resultant F1 hybrid of their initial (F1i) and reciprocal (F1r) cross. In the behavior front, we performed learning, memory, and anxiety stress-related tests to evaluate the overall mental health. We additionally performed several sensorimotor tests to assess the overall physical health of the mice. We observe heterotic inheritance in the hybrid mice in physical tests and different patterns of inheritance in sleep-wake patterns, social, anxiety and stress response. The catecholamine Norepinephrine (NE) helps regulate the abovementioned behaviors. Hence, we checked the levels of Tyrosine hydroxide (TH), the rate limiting enzyme in catecolamine synthesis, in different brain regions and found differential expression of TH in the brainstem of the four mice. Since Locus coeruleus (LC), located in the brainstem, is the major production centre of NE in the brain, we decided to investigate the differences in electric properties of LC neurons in the mice that could contribute to the differential behavior by the hybrid mice. We observe that the firing properties of the hybrid mice are different than their parental strains, which could be an influencing factor in the behavioral differences between the mice. RNA-seq and GO analysis of the whole-mouse-brain of B6, CAST, F1i, and F1r mice corroborated to some of the behaviors we observed. In addition, we performed RNA-seq of the Excitatory neurons and astrocytes cells of cortex of the hybrid mouse brain. We analyzed the data using bioinformatics tools and generated a list of potentially imprinted genes in specific cell types and have identified four novel cell-type-specific imprinted genes. Our multidisciplinary work allows us to appreciate the complex nature of the hybrid genome and the parental genome's contribution to the offsprings’ phenotype.