Fumio Mukai

Genotype of bovine sterol regulatory element binding protein-1 (SREBP-1) is associated with fatty acid composition in Japanese Black cattle

To investigate genetic factors that affect fatty acid composition in beef carcass, we previously investigated genetic profiles of stearoyl-CoA desaturase (SCD) and their effect on fatty acid composition in fat tissue of cattle. It has been known that sterol regulatory element binding protein (SREBP) is a transcription factor that regulates gene expression levels of SCD and other genes relevant to lipid and fatty acid metabolism in tissue. Therefore, we determined the full-length sequence of bovine SREBP-1 cDNA and then surveyed polymorphisms in whole exons and introns in the bovine genome. Large 84-bp insertion (long type: L) and deletion (short type: S) were found in intron 5 of bovine SREBP-1 in Japanese Black cattle, although there was no notable mutation in exon regions. The associations between the SREBP-1 genotypes and fatty acid compositions/fat melting points were analyzed by using genomic DNA with carcass trait information from 606 Japanese Black cattle. The S type contributed to 1.3% higher monounsaturated fatty acid (MUFA) proportion and 1.6°C lower melting point in intramuscular fat. Genotyping of bovine SREBP-1 is considered to reflect a genetic variation which is associated with physiologic characteristics of fat tissue in Japanese black cattle.

Association between fatty acid compositions and genotypes of FABP4 and LXR-alpha in Japanese Black cattle

BackgroundFatty acid composition has become an important trait in the beef industry in terms of beef flavor and decreasing the circulating concentration of LDL cholesterol. In this study, we examined the association between polymorphisms of six genes, adipocytes-type fatty acid binding protein (FABP4), liver X receptor α (LXRα), cytochrome b5 (Cyt b5), long-chain acyl-CoA synthetase (ACSL) 1, ACSL4 and diacylglycerol acyltransferase 2 (DGAT2) and fatty acid composition.ResultsSequence comparisons revealed 14 single nucleotide polymorphisms in six genes. Four of them, I74V and V110M in FABP4 and G51E and V133I in LXRα, were nonsynonymous substitutions. The associations between the genotypes and fatty acid compositions were analyzed by using 234 Japanese Black cattle. The genotypes of FABP4 I74V and LXRα V133I were significantly associated with palmitoleic acids (C16:1, P = 0.0086) and linoleic acid (C18:2, P = 0.0121) content in intramuscular fat, respectively.ConclusionOur findings suggest that the two polymorphisms of FABP4 I74V and LXRα V133I might be genetic factors in part associated with palmitoleic acid (FABP4 I74V) and linoleic acid (LXRα V133I) composition in intramuscular fat of Japanese Black cattle, respectively. Especially, FABP4 I74V had highly significant effect (P < 0.01) on C16:1 proportion, indicating that the I/I homozygote exhibited 0.5% higher percentage than V/V homozygote.

Heritabilities and genetic correlations of fatty acid compositions in longissimus muscle lipid with carcass traits in Japanese Black cattle

Fatty acid composition and carcass traits of 2,275 Japanese Black steers and heifers were analyzed to estimate the heritabilities and genetic correlations using the REML procedure. Slices of LM at the 6th to 7th rib section were minced and homogenized, and total lipids were extracted for the analysis by a gas chromatograph. Oleic acid accounted for the majority (51.3%), followed by palmitic (26.4%) and stearic (10.8%) acids. Heritabilities of carcass traits were moderate to high, ranging from 0.34 to 0.61, and heritabilities of individual fatty acids varied largely from 0.00 to 0.78. Those of MUFA, SFA, and PUFA were estimated to be 0.68, 0.66, and 0.47, respectively. Predicted breeding values for MUFA in 99 sires ranged from -3.0 to 5.4%. Genetic correlations of fatty acid compositions with carcass traits were generally weak (-0.28 to 0.39). Low but positive genetic correlations were obtained between beef marbling, on which emphasis of selection has been placed, and oleic acid (0.19) or MUFA (0.23). The results indicated the possibility not only for genetic improvement in fat quality traits but also simultaneous improvements with carcass traits by appropriate selection program.

Effect of SCD and SREBP genotypes on fatty acid composition in adipose tissue of Japanese Black cattle herds.

Fatty acid composition of beef adipose tissue is one of important traits because high proportions of monounsaturated fatty acid are related to favorable beef flavor and tenderness. In this study, we investigated effects of genetic factors such as stearoyl-CoA desaturase (SCD) and sterol regulatory element binding protein (SREBP) on beef carcass traits including fatty acid composition using two cattle populations. Sire effect was significantly related to almost all traits except BMS, suggesting that the trait examined in this study is highly controlled by genetic factors. The effect of SCD genotype on fatty acid composition was detected remarkably in both cattle groups, especially on stearic and oleic acids. This result was consistent with our previous studies and suggests that SCD is associated with fatty acid composition. Unlike SCD genotyping, the effect of SREBP genotype was not identified in this study. Our results suggested that SCD genotype would contribute to improving beef quality in field populations. Further studies about the relationship among these factors will bring an insight into the molecular mechanism of fatty acid metabolism in cattle.

The ubiquitin ligase gene (WWP1) is responsible for the chicken muscular dystrophy

Chicken muscular dystrophy with abnormal muscle (AM) has been studied for more than 50 years, but the gene responsible for it remains unclear. Our previous studies narrowed down the AM candidate region to approximately 1 Mbp of chicken chromosome 2q containing seven genes. In this study, we performed sequence comparison and gene expression analysis to elucidate the responsible gene. One missense mutation was detected in AM candidate genes, while no remarkable alteration of expression patterns was observed. The mutation was identified in WWP1, detected only in dystrophic chickens within several tetrapods. These results suggested WWP1 is responsible for chicken muscular dystrophy.

Reduction of inbreeding in commercial females by rotational mating with several sire lines

A mating system to reduce the inbreeding of commercial females in the lower level was examined theoretically, assuming a hierarchical breed structure, in which favorable genes are accumulated in the upper level by artificial selection and the achieved genetic progress is transferred to the lower level through migration of males. The mating system examined was rotational mating with several closed sire lines in the upper level. Using the group coancestry theory, we derived recurrence equations for the inbreeding coefficient of the commercial females. The asymptotic inbreeding coefficient was also derived. Numerical computations showed that the critical factor for determining the inbreeding is the number of sire lines, and that the size of each sire line has a marginal effect. If four or five sire lines were available, rotational mating was found to be quite an effective system to reduce the short- and long-term inbreeding of the commercial females, irrespective of the effective size of each sire line. Oscillation of the inbreeding coefficient under rotational mating with initially related sire lines could be minimized by avoiding the consecutive use of highly related lines. Extensions and perspectives of the system are discussed in relation to practical application.

Genetic structure and relationships of 16 Asian and European cattle populations using DigiTag2 assay

Abstract In this study, we genotyped 117 autosomal single nucleotide polymorphisms using a DigiTag2 assay to assess the genetic diversity, structure and relationships of 16 Eurasian cattle populations, including nine cattle breeds and seven native cattle. Phylogenetic and principal component analyses showed that Bos taurus and Bos indicus populations were clearly distinguished, whereas Japanese Shorthorn and Japanese Polled clustered with European populations. Furthermore, STRUCTURE analysis demonstrated the distinct separation between Bos taurus and Bos indicus (K=2), and between European and Asian populations (K=3). In addition, Japanese Holstein exhibited an admixture pattern with Asian and European cattle (K=3‐5). Mongolian (K=13‐16) and Japanese Black (K=14‐16) populations exhibited admixture patterns with different ancestries. Bos indicus populations exhibited a uniform genetic structure at K=2‐11, thereby suggesting that there are close genetic relationships among Bos indicus populations. However, the Bhutan and Bangladesh populations formed a cluster distinct from the other Bos indicus populations at K=12‐16. In conclusion, our study could sufficiently explain the genetic construction of Asian cattle populations, including: (i) the close genetic relationships among Bos indicus populations; (ii) the genetic influences of European breeds on Japanese breeds; (iii) the genetic admixture in Japanese Holstein, Mongolian and Japanese Black cattle; and (iv) the genetic subpopulations in Southeast Asia.

Low mitochondrial DNA diversity of Japanese Polled and Kuchinoshima feral cattle

This study aims to estimate the mitochondrial genetic diversity and structure of Japanese Polled and Kuchinoshima feral cattle, which are maintained in small populations. We determined the mitochondrial DMA (mtDNA) displacement loop (D-loop) sequences for both cattle populations and analyzed these in conjunction with previously published data from Northeast Asian cattle populations. Our findings showed that Japanese native cattle have a predominant, Asian-specific mtDNA haplogroup T4 with high frequencies (0.43-0.81). This excluded Kuchinoshima cattle (32 animals), which had only one mtDNA haplotype belonging to the haplogroup T3. Japanese Polled showed relatively lower mtDNA diversity in the average sequence divergence (0.0020) than other Wagyu breeds (0.0036-0.0047). Japanese Polled have been maintained in a limited area of Yamaguchi, and the population size is now less than 200. Therefore, low mtDNA diversity in the Japanese Polled could be explained by the decreasing population size in the last three decades. We found low mtDNA diversity in both Japanese Polled and Kuchinoshima cattle. The genetic information obtained in this study will be useful for maintaining these populations and for understanding the origin of Japanese native cattle.

Determination of Optimum Mating Design With Constraints on Inbreeding Level via a Simple Genetic Algorithm

予測育種価を用いた選抜は,集団の近交度を急激に上昇させる危険性をともなうため,遺伝的アルゴリズム(GAs)を用いて近交度に制限を加えた交配計画の最適化を試みた.GAsとは,「染色体」が「交叉」し「遺伝子」が「突然変異」を起こしながら「適応度」の高い個体が生き残っていく進化の過程を模倣して最適解を探索するアルゴリズムである.近交度に制限を加えない状況でGAの探索能力を検討した結果,染色体数および交叉回数のオペレーターの影響はほとんど認められなかった.しかし,突然変異率が減少するにつれ,GAの探索能力は向上した.近交に制限を加えて交配計画の最適化を試みたところ,過剰な近交度を示した染色体,すなわち交配計画に適切なペナルティーを与えてやれば,GAにより妥当な交配計画が探索された.ペナルティーの大きさはGAが探索できる解空間の大きさに依存するなど,GAの実際の適用には,オペレーターの決定にさらなる研究が必要であるが,有効な方法となりうることが明らかになった.

Prediction of Direct Response and Its Correlated Response Under Selection on Predicted Breeding Values

これまでの選抜反応の予測式は,すべての個体が同一の正確度を持つとの仮定によって導かれてきているが,BLUP法で予測される育種価は各個体が記録の有無や血縁個体からの情報量により異なった正確度を持つ.したがって本報告では,個体ごとに選抜の正確度が異なる状況を想定し,直接ならびに間接選抜反応を予測する3種の予測式をシミュレーションにより比較した.予測式としては,1) 従来の予測式の選抜の正確度を,育種価予測値の正確度の平均値に置き換えた予測式(AA),2) 選抜対象集団を育種価予測値の正確度によりグループ化し,それぞれのグループから重みづけした改良量を算出する予測式(GA)および3) 育種価予測値の選抜差(SP)の3種を用いた.直接選抜反応を予測する場合,予測式間の差は小さかったが,AAの間接選抜反応は真値を大きく過小評価した.一般に本報告でシミュレートした集団のように,育種価予測値とその正確度に関連性が認められない状況では,間接選抜反応においてSPはGAより優れた予測精度を示すことが認められた.