Choong-Gon Kim

DNA sequence and comparative analysis of chimpanzee chromosome 22

Human–chimpanzee comparative genome research is essential for narrowing down genetic changes involved in the acquisition of unique human features, such as highly developed cognitive functions, bipedalism or the use of complex language. Here, we report the high-quality DNA sequence of 33.3 megabases of chimpanzee chromosome 22. By comparing the whole sequence with the human counterpart, chromosome 21, we found that 1.44% of the chromosome consists of single-base substitutions in addition to nearly 68,000 insertions or deletions. These differences are sufficient to generate changes in most of the proteins. Indeed, 83% of the 231 coding sequences, including functionally important genes, show differences at the amino acid sequence level. Furthermore, we demonstrate different expansion of particular subfamilies of retrotransposons between the lineages, suggesting different impacts of retrotranspositions on human and chimpanzee evolution. The genomic changes after speciation and their biological consequences seem more complex than originally hypothesized.Human–chimpanzee comparative genome research is essential for narrowing down genetic changes involved in the acquisition of unique human features, such as highly developed cognitive functions, bipedalism or the use of complex language. Here, we report the high-quality DNA sequence of 33.3 megabases of chimpanzee chromosome 22. By comparing the whole sequence with the human counterpart, chromosome 21, we found that 1.44% of the chromosome consists of single-base substitutions in addition to nearly 68,000 insertions or deletions. These differences are sufficient to generate changes in most of the proteins. Indeed, 83% of the 231 coding sequences, including functionally important genes, show differences at the amino acid sequence level. Furthermore, we demonstrate different expansion of particular subfamilies of retrotransposons between the lineages, suggesting different impacts of retrotranspositions on human and chimpanzee evolution. The genomic changes after speciation and their biological consequences seem more complex than originally hypothesized.

Construction of a gorilla fosmid library and its PCR screening system

A gorilla fosmid library of 261,120 independent clones was constructed and characterized. The fosmid vector is similar to the cosmid in average insert size of ca. 40 kb but contains the F factor for replication, and it is more resistant to recombination. This clone library represents about 3.7 times coverage of the gorilla genome. A simple screening system by PCR was established, and we successfully found 9 clones that cover the entire Hox A gene cluster of the gorilla genome. This gorilla fosmid DNA library is a useful resource for comparative genomics of human and apes.

Molecular characterization, gene expression analysis and biochemical properties of α-amylase from the disk abalone, Haliotis discus discus.

The present study reports the molecular characterization, cloning, expression, and biochemical characterization of alpha-amylase identified from the disk abalone, Haliotis discus discus cDNA library. The full length of the alpha-amylase cDNA was 1650 bp, and it encoded a polypeptide of 511 amino acids. The predicted HdAmyI molecular mass of mature protein was 54 kDa and the estimated isoelectric point (pI) was 8.3. The alpha-amylase gene showed its characteristic motifs, catalytic sites, substrate binding sites and conserved regions with other known species of alpha-amylases. Purified recombinant HdAmyI exhibited a relatively low activity of 0.1 U/mg protein towards 1% starch. HdAmyI had an optimum temperature and pH of 50 degrees C and 6.5, respectively. It also demonstrated stability in a wide range of temperatures and pH. Tissue-specific mRNA expression results showed that HdAmyI is expressed only in the digestive tract and hepatopancreas, with the highest levels in the hepatopancreas. Over 8 weeks of starvation, alpha-amylase transcription was decreased significantly relative to basal levels. However, after starvation, mRNA transcription was increased and returned to normal level by the 2nd week of feeding, suggesting that the alpha-amylase mRNA expression changes according to variations in food availability at the transcriptional level in disk abalone.

Nucleotide sequence comparison of a chromosome rearrangement on human chromosome 12 and the corresponding ape chromosomes

Chromosome rearrangement has been considered to be important in the evolutionary process. Here, we demonstrate the evolutionary relationship of the rearranged human chromosome 12 and the corresponding chromosome XII in apes (chimpanzee, bonobo, gorilla, orangutan, and gibbon) by examining PCR products derived from the breakpoints of inversions and by conducting shotgun sequencing of a gorilla fosmid clone containing the breakpoint and a “duplicated segment” (duplicon). We confirmed that a pair of 23-kb duplicons flank the breakpoints of inversions on the long and short arms of chimpanzee chromosome XII. Although only the 23-kb duplicon on the long arm of chimpanzee chromosome XII and its telomeric flanking sequence are found to be conserved among the hominoids (human, great apes, and gibbons), the duplicon on the short arm of chimpanzee chromosome XII is suggested to be the result of a duplication from that on the long arm. Furthermore, the shotgun sequencing of a gorilla fosmid indicated that the breakpoint on the long arm of the gorilla is located at a different position 1.9 kb from that of chimpanzee. The region is flanked by a sequence homologous to that of human chromosome 6q22. Our findings and sequence analysis suggest a close relationship between segmental duplication and chromosome rearrangement (or breakpoint of inversion) in Hominoidea. The role of the chromosome rearrangement in speciation is also discussed based on our new results.

The complete mitochondrial genome of the marine polychaete: Perinereis aibuhitensis (Phyllodocida, Nereididae)

Abstract We determined the complete mitochondrial genome sequence of the marine polychaete Perinereis aibuhitensis (Grube, 1878) (Phyllodocida, Nereididae), a dominant species in the mudflat of the West Pacific and Indian Ocean. The complete genome of P. aibuhitensis is 15,852 bp in size including 13 protein coding genes (PCGs), 2 rRNA and 22 tRNA with the same gene order and structure as those of other Nereididae species. The nucleotide composition is 29.5% A, 21.2% C, 14.1% G, 35.2% T, showing a high content of A + T with G being used least in the third codon position (6.7%). All PCGs use ATG as the start codon while for the stop codon COI and ND1 use incomplete codon of T. The mitogenome sequence of P. aibuhitensis is second to that of P. nuntia known in the genus Perinereis, which will provide useful information for understanding evolutionary history of the genus Perinereis within the family Nereididae.

Complete mitochondrial genome of the mottled skate: Raja pulchra (Rajiformes, Rajidae)

Abstract The complete sequence of mitochondrial DNA of a mottled skate, Raja pulchra was sequenced as being circular molecules of 16,907 bp including 2 rRNA, 22 tRNA, 13 protein-coding genes (PCGs), and an AT-rich control region. The organization of the PCGs is the same as those found in other Rajidae species. The nucleotide of L-strand is composed of 29.8% A, 28.0% C, 27.9% T, and 14.3% G with a bias toward A + T slightly. Twelve of 13 PCGs are initiated by the ATG codon while COX1 starts with GTG. Only ND4 harbors the incomplete termination codon, TA. All tRNA genes have a typical clover-leaf structure of mitochondrial tRNA with the exception of which has a reduced DHU arm. This mitogenome will provide essential information for better phylogenetic resolution and precision of the family Rajidae and the genus Raja as well as for establishment of a fish stock recovery plan of the species.

No Distinction of Orthology/Paralogy between Human and Chimpanzee Rh Blood Group Genes

On human (Homo sapiens) chromosome 1, there is a tandem duplication encompassing Rh blood group genes (Hosa_RHD and Hosa_RHCE). This duplication occurred in the common ancestor of humans, chimpanzees (Pan troglodytes), and gorillas, after splitting from their common ancestor with orangutans. Although several studies have been conducted on ape Rh blood group genes, the clear genome structures of the gene clusters remain unknown. Here, we determined the genome structure of the gene cluster of chimpanzee Rh genes by sequencing five BAC (Bacterial Artificial Chromosome) clones derived from chimpanzees. We characterized three complete loci (Patr_RHα, Patr_RHβ, and Patr_RHγ). In the Patr_RHβ locus, a short version of the gene, which lacked the middle part containing exons 4–8, was observed. The Patr_RHα and Patr_RHβ genes were located on the locations corresponding to Hosa_RHD and Hosa_RHCE, respectively, and Patr_RHγ was in the immediate vicinity of Patr_RHβ. Sequence comparisons revealed high sequence similarity between Patr_RHβ and Hosa_RHCE, while the chimpanzee Rh gene closest to Hosa_RHD was not Patr_RHα but rather Patr_RHγ. The results suggest that rearrangements and gene conversions frequently occurred between these genes and that the classic orthology/paralogy dichotomy no longer holds between human and chimpanzee Rh blood group genes.

Complete mitochondrial genome sequence of Heliocidaris crassispina (Camarodonta, Echinometridae).

Abstract The whole mitochondrial genome sequence of sea urchin Heliocidaris crassispina of the family Echinometridae is determined for the first time in this study. The circular mitogenome (15,702 bp) consists of typical Camarodonta gene order and its components including 2 rRNA, 22 tRNA, 13 protein-coding genes and a control region. Phylogenetic analysis based on the 13 concatenated protein-coding gene sequences shows that H. crassispina is closer to the species of Strongylocentrotidae than Parechinidae, but the separation between H. crassispina and the Strongylocentrotid species occurred early in their evolution. The complete mitochondrial genome presented in this study is useful for inferring the phylogenetic relationship among the families of Echinidea sea urchins.

Complete mitochondrial genome of the Kwangtung skate: Dipturus kwangtungensis (Rajiformes, Rajidae)

Abstract The complete sequence of mitochondrial DNA of a Kwangtung skate, Dipturus kwangtungensis, was determined as being circular molecules of 16,912 bp including 2 rRNA, 22 tRNA, 13 protein coding genes (PCGs) and a control region. The arrangement of the PCGs is the same as that found in other Rajidae species. The nucleotide of L-strand which encodes most of the proteins is composed of 30.2% A, 27.4% C, 28.2% T and 14.2% G with a bias toward A+T slightly. Twelve of 13 PCGs are initiated by the ATG codon while COX1 starts with GTG. Only ND4 harbors the incomplete termination codon, TA. All tRNA genes have a typical clover-leaf structure of mitochondrial tRNA with the exception of tRNASerAGY, which has a reduced DHU arm. This mitogenome is the first report for a species of the genus Dipturus, which will become an important source of information on the phylogenetic relationship and the evolution of the genus Dipturus within the family Rajidae.

The complete mitochondrial genome of the Korean skate: Hongeo koreana (Rajiformes, Rajidae)

Abstract The complete mitochondrial genome of the Korean skate, Hongeo koreana, the sole member of its genus, is investigated for the first time. The genome consists of 16,906 bp in length including 2 rRNA, 22 tRNA and 13 protein coding genes with the same gene order and structure of the genome as those of other Rajidae species. The overall nucleotide composition of the L-strand is A = 29.8%, C = 27.9%, T = 27.9% and G = 14.3%, showing a high A + T bias. The anti-G bias (6.0%) is more significant in the third codon position. Twelve of the 13 protein-coding genes use ATG as their start codon while the COX1 gene starts with GTG. For stop codon, ND3 and ND4 genes show incomplete stop codon T. The mitogenome sequence of H. koreana will provide important information on the evolution and the phylogenetic relation of the genus Hongeo in relation to the other genera of the family Rajidae.