Publications by authors named "Akihiko Koga"

Objective: The remarkable adaptability to the environment, high growth rate, meat with good taste and aroma, and ornamental appearance of the Pradu Hang Dam (PDH) and Samae Dam (SD) chickens make them valuable for improvement of poultry production to enhance food security. However, despite their close phenotypic similarity, distinct classification of PDH and SD chickens remains controversial. Thus, this study aimed to clarify genetic origins and variation between PDH and SD chickens, genetic diversity and structures of PDH and SD chickens.

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Originating in Thailand, the Thai Ridgeback dog is known for its unique fur ridge that grows in the opposite direction along its back. Selective breeding and a limited populations in Thailand have led to significant close inbreeding among related individuals. The current Thai Ridgeback population is assumed to have experienced a loss of genetic diversity and bottleneck events.

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  • - Hybrid sterility in catfish occurs due to differences in parental genomes affecting meiosis, which is crucial for reproduction.
  • - The study focused on bighead catfish and North African catfish, analyzing their genome divergence and meiotic behavior to understand sterility in their male hybrids.
  • - Results indicated that significant differences in satellite DNA (satDNA) between the parent species are likely responsible for meiotic failure, rather than differences in chromosome numbers.
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High levels of purine and uric acid, which are associated with health issues such as gout and cardiovascular disease, are found in the meat of fast-growing broiler chickens, which raises concerns about the quality of chicken meat and the health of the consumers who consume it. High genetic homogeneity and uniformity, particularly in genes involved in the synthesis of inosine monophosphate (IMP) and subsequent process of purine synthesis, which are associated with the meat quality, are exhibited in commercial broiler chickens owing to intensive inbreeding programs. Adenosine succinate lyase (ADSL) is a key enzyme involved in de novo purine biosynthetic pathway and its genetic polymorphisms affect IMP metabolism and purine content.

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  • The North African catfish (Clarias gariepinus) is important for aquaculture and food security, but closed breeding practices have reduced its reproductive performance, likely due to inbreeding depression.
  • A study assessed the genetic diversity of catfish populations in Thailand using microsatellite genotyping and mitochondrial DNA sequencing, revealing low inbreeding coefficients and significant genetic diversity across three populations.
  • The findings suggest that introducing new, well-documented populations into breeding programs could enhance genetic improvement and productivity of the North African catfish.
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The thermal stress caused by global climate change adversely affects the welfare, productivity, and reproductive performance of farm animals, including chickens, and causes substantial economic losses. However, the understanding of the genetic basis of the indigenous chicken adaptation to high ambient temperatures is limited. Hence, to reveal the genetic basis of thermal stress adaptation in chickens, this study investigated polymorphisms in the heat shock protein 70 (HSP70) and HSP90 genes, known mechanisms of cellular defense against thermal stress in indigenous and local chicken breeds and red junglefowls in Thailand.

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Eukaryotes have varying numbers and structures of characteristic chromosomes across lineages or species. The evolutionary trajectory of species may have been affected by spontaneous genome rearrangements. Chromosome fusion drastically alters karyotypes.

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  • The study focused on identifying sex-specific and linked loci in the Siamese cobra using in silico chromosome mapping, derived from the Indian cobra genome.
  • A total of 475 loci were mapped, with 227 located on the Z sex chromosome, suggesting a potential sex-determining region.
  • One specific locus, PA100000600, is linked to the TOPBP1 gene, which may be associated with male infertility due to meiotic defects, shedding light on genetic aspects of sex traits in snakes.
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Background: In nucleotide public repositories, studies discovered data errors which resulted in incorrect species identification of several accipitrid raptors considered for conservation. Mislabeling, particularly in cases of cryptic species complexes and closely related species, which were identified based on morphological characteristics, was discovered. Prioritizing accurate species labeling, morphological taxonomy, and voucher documentation is crucial to rectify spurious data.

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  • * Previous tests suggested undetected walbRep sequences in the tammar wallaby due to primer issues; however, studies using an updated genome database found that walb exists as separate segments rather than tandem repeats.
  • * Conclusively, walbRep likely formed after the red-necked wallaby diverged from the tammar wallaby, and researchers identified a uniquely structured walb copy, proposing a model for how it was generated.
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Microsatellites are polymorphic and cost-effective. Optimizing reduced microsatellite panels using heuristic algorithms eases budget constraints in genetic diversity and population genetic assessments. Microsatellite marker efficiency is strongly associated with its polymorphism and is quantified as the polymorphic information content ().

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DNA barcoding without assessing reliability and validity causes taxonomic errors of species identification, which is responsible for disruptions of their conservation and aquaculture industry. Although DNA barcoding facilitates molecular identification and phylogenetic analysis of species, its availability in clariid catfish lineage remains uncertain. In this study, DNA barcoding was developed and validated for clariid catfish.

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Microsatellites are short tandem DNA repeats, ubiquitous in genomes. They are believed to be under selection pressure, considering their high distribution and abundance beyond chance or random accumulation. However, limited analysis of microsatellites in single taxonomic groups makes it challenging to understand their evolutionary significance across taxonomic boundaries.

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The kangaroo endogenous retrovirus (KERV) was previously reported to have undergone a rapid copy number increase in the red-necked wallaby; however, the mode of amplification was left to be clarified. The present study revealed that the long terminal repeat (LTR) (0.6 kb) and internal region (2.

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We recently identified walbRep, a satellite DNA residing in the genome of the red-necked wallaby Notamacropus rufogriseus. It originates from the walb endogenous retrovirus and is organized in a manner in which the provirus structure is retained. The walbRep repeat units feature an average pairwise nucleotide identity as high as 99.

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Long terminal repeat (LTR) retroelements, including endogenous retroviruses, are one of the origins of satellite DNAs. However, the vast majority of satellite DNAs originating from LTR retroelements consists of parts of the element. In addition, they frequently contain sequences unrelated to that element.

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An albino infant wallaby was born to a mother with wild-type body color. PCR and sequencing analyses of (encoding tyrosinase, which is essential for melanin biosynthesis) of this albino wallaby revealed a 7.1-kb-long DNA fragment inserted in the first exon.

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  • Alpha satellite DNA is crucial for primate centromeres, with Azara's owl monkey featuring two types: OwlAlp1 and OwlAlp2.
  • Research indicates that OwlAlp1 likely replaced OwlAlp2 as the centromeric DNA due to its binding with the CENP-A protein, although the evolutionary details of this change are still unclear.
  • A phylogenetic analysis revealed that OwlAlp1 is more closely related to OwlAlp2 than to other primate alpha satellite DNAs, showing recent rapid expansion in the owl monkey lineage potentially linked to its adaptation to a nocturnal lifestyle.
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The majority of DNA-based transposable elements comprise autonomous and nonautonomous copies, or only nonautonomous copies, where the autonomous copy contains an intact gene for a transposase protein and the nonautonomous copy does not. Even if autonomous copies coexist, they are generally less frequent. The element of medaka fish is one of the few elements for which a nonautonomous copy has not yet been found.

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Albino mutants (white coat and red eyes) of tanuki (Nyctereutes procyonoides viverrinus) have been repeatedly found in the Central Alps area of Japan. We recently reported that an albino tanuki from Iida, a city in this area, lacks the third exon of the TYR gene encoding tyrosinase, which is essential for melanin synthesis. The absence of this exon was due to the chromosomal deletion of a complex structure.

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  • In nocturnal mammals, rod cells have heterochromatin in the nucleus that helps efficiently direct light to photoreceptors.
  • The study focused on owl monkeys, particularly the species Aotus azarae, which was found to have a similar heterochromatin structure in its rod cells.
  • Analysis of another species, Aotus lemurinus, confirmed they also possess this feature, suggesting the heterochromatin block formed before the two species diverged, estimated to have occurred around 15 million years ago.
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Tanuki (), or Japanese raccoon dog, is a canine native to Japan. Tanuki with complete oculocutaneous albinism are relatively frequent in mountainous areas of mainland Japan. Tyrosinase, which is encoded by the gene, is an enzyme essential for the biosynthesis of melanin pigment.

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An infant hamadryas baboon exhibiting an albino phenotype-white body hair and red eyes-was born to parents with wild-type body color. Pigmentation on some parts of its body surfaced during childhood and progressed with age. This baboon in adulthood has gray hair on parts of its body, such as the tail, distal portion of the legs, and face, with the remainder being white.

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Centromere protein B (CENP-B), a protein participating in centromere formation, binds to centromere satellite DNA by recognizing a 17-bp motif called the CENP-B box. This motif is found in hominids (humans and great apes) at an identical location in repeat units of their centromere satellite DNA. We have recently reported that the CENP-B box exists at diverse locations in three New World monkey species (marmoset, squirrel monkey and tamarin).

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African great apes have large constitutive heterochromatin (C-band) blocks in subtelomeric regions of the majority of their chromosomes, but humans lack these. Additionally, the chimpanzee meiotic cell division process demonstrates unique partial terminal associations in the first meiotic prophase (pachytene). These are likely formed as a result of interaction among subtelomeric C-band blocks.

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