Hominoid evolution as judged by fibrinopeptide structures

Genomic Comparisons of Humans and Chimpanzees

The genome consists of the entire DNA present in the nucleus of the fertilized embryo, which is then duplicated in every cell in the body. A draft sequence of the chimpanzee genome is now available, providing opportunities to better understand genetic contributions to human evolution, development, and disease. Sequence differences from the human genome were confirmed to be ∼1% in areas that can be precisely aligned, representing ∼35 million single base-pair differences. Some 45 million nucleotides of insertions and deletions unique to each lineage were also discovered, making the actual difference between the two genomes ∼4%. We discuss the opportunities and challenges that arise from this information and the need for comparison with additional species, as well as population genetic studies. Finally, we present a few examples of interesting findings resulting from genome-wide analyses, candidate gene studies, and combined approaches, emphasizing the pros and cons of each approach.

Sequencing the chimpanzee genome: insights into human evolution and disease

Large-scale sequencing of the chimpanzee genome is now imminent. Beyond the inherent fascination of comparing the sequence of the human genome with that of our closest living relative, this project is likely to yield tangible scientific benefits in two areas. First, the discovery of functionally important mutations that are specific to the human lineage offers a new path towards medical benefits. Second, chimpanzee-human comparisons are likely to yield molecular insights into how new biological characteristics evolve--findings that might be relevant throughout the tree of life.

The beta(2) subunit of soluble guanylyl cyclase contains a human-specific frameshift and is expressed in gastric carcinoma

Soluble or nitric oxide (NO) stimulated guanylyl cyclases are obligate heme-containing heterodimers (alpha/beta). We report the full-length cDNA of the human ortholog of the rat beta(2)-subunit from human kidney. A database search yielded matches of the 3' non-coding sequence with previously unassigned expressed sequence tags from kidney and stomach signet ring cell carcinoma. PCR comparison of cDNA from stomach signet ring cell carcinoma and normal stomach tissue demonstrated beta(2) subunit expression in cancer but not in normal tissue. On the cDNA level a frameshift deletion of one nucleotide was present in the novel human sequence which was confirmed on the genomic DNA level. In four closely related nonhuman primate species the frameshift deletion was absent while analysis of genomic DNA from different ethnic backgrounds revealed the uniform presence of the frameshift deletion in the human population.

A structural difference between the cell surfaces of humans and the great apes

The sialic acids are major components of the cell surfaces of animals of the deuterostome lineage. Earlier studies suggested that humans may not express N-glycolyl-neuraminic acid (Neu5Gc), a hydroxylated form of the common sialic acid N-acetyl-neuraminic acid (Neu5Ac). We find that while Neu5Gc is essentially undetectable on human plasma proteins and erythrocytes, it is a major component in all the four extant great apes (chimpanzee, bonobo, gorilla and orangutan) as well as in many other mammals. This marked difference is also seen amongst cultured lymphoblastoid cells from humans and great apes, as well as in a variety of other tissues compared between humans and chimpanzees, including the cerebral cortex and the cerebrospinal fluid. Biosynthetically, Neu5Gc arises from the action of a hydroxylase that converts the nucleotide donor CMP-Neu5Ac to CMP-Neu5Gc. This enzymatic activity is present in chimpanzee cells, but not in human cells. However, traces of Neu5Gc occur in some human tissues, and others have reported expression of Neu5Gc in human cancers and fetal tissues. Thus, the enzymatic capacity to express Neu5Gc appears to have been suppressed sometime after the great ape-hominid divergence. As terminal structures on cell surfaces, sialic acids are involved in intercellular cross-talk involving specific vertebrate lectins, as well as in microbe-host recognition involving a wide variety of pathogens. The level of sialic acid hydroxylation (level of Neu5Ac versus Neu5Gc) is known to positively or negatively affect several of these endogenous and exogenous interactions. Thus, there are potential functional consequences of this widespread structural change in humans affecting the surfaces of cells throughout the body.

A mutation in human CMP-sialic acid hydroxylase occurred after the Homo-Pan divergence

Sialic acids are important cell-surface molecules of animals in the deuterostome lineage. Although humans do not express easily detectable amounts of N-glycolylneuraminic acid (Neu5Gc, a hydroxylated form of the common sialic acid N-acetylneuraminic acid, Neu5Ac), it is a major component in great ape tissues, except in the brain. This difference correlates with lack of the hydroxylase activity that converts CMP-Neu5Ac to CMP-Neu5Gc. Here we report cloning of human and chimpanzee hydroxylase cDNAs. Although this chimpanzee cDNA is similar to the murine homologue, the human cDNA contains a 92-bp deletion resulting in a frameshift mutation. The isolated human gene also shows evidence for this deletion. Genomic PCR analysis indicates that this deletion does not occur in any of the African great apes. The gene is localized to 6p22-p23 in both humans and great apes, which does not correspond to known chromosomal rearrangements that occurred during hominoid evolution. Thus, the lineage leading to modern humans suffered a mutation sometime after the common ancestor with the chimpanzee and bonobo, potentially affecting recognition by a variety of endogenous and exogenous sialic acid-binding lectins. Also, the expression of Neu5Gc previously reported in human fetuses and tumors as well as the traces detected in some normal adult humans must be mediated by an alternate pathway.

Penguin evolution: protein comparisons demonstrate phylogenetic relationship to flying aquatic birds

Quantitative immunological comparisons of three avian proteins, transferrin, ovalbumin, and penalbumin, indicate that penguins are phylogenetically most closely related to loons, albatrosses, herons, and grebes. These data support the theory that the ancestors of penguins were flying oceanic birds and that flightlessness in penguins has evolved independently from flightlessness in ratites.

The myoglobin of primates. VIII. Gorilla gorilla beringei (eastern highland gorilla)

On aligning the tryptic peptides of the myoglobin from a gorilla with the homologous human peptides, one amino acid difference was found. By dansyl-Edman degradation this was shown to be at position 22, i.e. at a position other than those where man, chimpanzee and gibbon differ from one another.