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Compared with our closest living evolutionary cousins, humans appear unusually prone to develop carcinomas (cancers arising from epithelia). The SIGLEC12 gene, which encodes the Siglec‐XII protein expressed on epithelial cells, has several uniquely human features: a fixed homozygous missense mutation inactivating its natural ligand recognition property; a polymorphic frameshift mutation eliminating full‐length protein expression in ~60%–70% of worldwide human populations; and, genomic features suggesting a negative selective sweep favoring the pseudogene state. Despite the loss of canonical sialic acid binding, Siglec‐XII still recruits Shp2 and accelerates tumor growth in a mouse model. We hypothesized that dysfunctional Siglec‐XII facilitates human carcinoma progression, correlating with known tumorigenic signatures of Shp2‐dependent cancers. Immunohistochemistry was used to detect Siglec‐XII expression on tissue microarrays. PC‐3 prostate cancer cells were transfected with Siglec‐XII and transcription of genes enriched with Siglec‐XII was determined. Genomic SIGLEC12 status was determined for four different cancer cohorts. Finally, a dot blot analysis of human urinary epithelial cells was established to determine the Siglec‐XII expressors versus non‐expressors. Forced expression in a SIGLEC12 null carcinoma cell line enriched transcription of genes associated with cancer progression. While Siglec‐XII was detected as expected in ~30%–40% of normal epithelia, ~80% of advanced carcinomas showed strong expression. Notably, >80% of late‐stage colorectal cancers had a functional SIGLEC12 allele, correlating with overall increased mortality. Thus, advanced carcinomas are much more likely to occur in individuals whose genomes have an intact SIGLEC12 gene, likely because the encoded Siglec‐XII protein recruits Shp2‐related oncogenic pathways. The finding has prognostic, diagnostic, and therapeutic implications.

O-Mannose glycans, a family of highly heterogeneous complex glycans account up to 30% of total O-glycans in brain. Previous synthesis and functional studies only focused on the Core M3 O-mannose glycans of α-dystroglycan which are a causative factor for various muscular diseases. In this study, a highly efficient chemoenzymatic strategy was developed that enabled the first collective synthesis of 63 Core M1 and Core M2 O-mannose glycans. This chemoenzymatic strategy features the gram-scale chemical synthesis of 5 judiciously designed core structures, and the diversity-oriented modification of the core structures with 3 enzyme modules to provide 58 complex O-mannose glycans in a linear sequence that does not exceed 4 steps. Of note, 55 of these O-mannose glycans are synthesized for the first time. Using the printed O-mannose glycan array, the human brain protein CD33, a key factor in the modulation of Alzheimer’s disease was identified as strongly binding to sialylated Core M1 and Core M2.

Author(s): Do, Raymond | Advisor(s): Varki, Nissi M | Abstract: The primate SIGLEC12 gene encodes one of the CD33-related Siglec family of signaling molecules in immune cells. Siglecs are normally expressed on hematopoietic cells. Interestingly, it was previously reported that the human SIGLEC12 gene product Siglec-XII is expressed on some epithelium and also on prostate carcinomas. Stably transfected Siglec-XII-expressing prostate cancer cells demonstrated altered regulation of several genes associated with carcinoma progression, as well as enhanced growth in nude mice. However, SIGLEC12 allele status did not predict prostate carcinoma incidence. Here, we confirm and expand on previous immunohistochemical analysis of Siglec-XII expression in human epithelium, and found that Siglec-XII expression correlates with an increased risk of late stage carcinoma development. While no significant correlation was found between Siglec-XII expression and incidence of early stage or slow progressing cancers in two patient cohorts, we found that Siglec-XII expression is correlated with a significantly increased rate of late stage carcinoma progression in a late stage colorectal carcinoma patient cohort. We also found through RNA-Seq analysis that several genes associated with cancer progression are differentially expressed in a stably transfected PC-3 Siglec-XII expressing cell line. Finally, we propose a unique new noninvasive test, a dot blot using urine samples which may become a screening test for the efficient determination of an individual’s Siglec-XII status. This test may thus become useful as a diagnostic screen in the future. Thus, polymorphic expression of Siglec-XII in humans may determine progression of certain late stage carcinomas.

In our paper we contribute to the burgeoning literature in the psychology of debt repayment. Across three experiments, we explore the effects of the type (hedonic or utilitarian) and the timing of debt on consumers' debt repayment when managing multiple debt accounts. While prior literature has demonstrated that debtors who own multiple credit cards behave irrationally by paying down smaller balances rather than balances with higher interest rates, we found that debts incurred for hedonic purchases and in the distant past (versus proximal past) amplify this effect. The anticipated impact of debt repayment on consumption enjoyment is found to mediate this effect.

Heart disease is common in both humans and chimpanzees, manifesting typically as sudden cardiac arrest or progressive heart failure. Surprisingly, although chimpanzees are our closest evolutionary relatives, the major cause of heart disease is different in the two species. Histopathology data of affected chimpanzee hearts from two primate centers, and analysis of literature indicate that sudden death in chimpanzees (and in gorillas and orangutans) is commonly associated with diffuse interstitial myocardial fibrosis of unknown cause. In contrast, most human heart disease results from coronary artery atherosclerosis, which occludes myocardial blood supply, causing ischemic damage. The typical myocardial infarction of humans due to coronary artery thrombosis is rare in these apes, despite their human-like coronary-risk-prone blood lipid profiles. Instead, chimpanzee ‘heart attacks’ are likely due to arrythmias triggered by myocardial fibrosis. Why do humans not often suffer from the fibrotic heart disease so common in our closest evolutionary cousins? Conversely, why do chimpanzees not have the kind of heart disease so common in humans? The answers could be of value to medical care, as well as to understanding human evolution. A preliminary attempt is made to explore possibilities at the histological level, with a focus on glycosylation changes.

Sialic acids (Sias) are a group of α-keto acids with a nine-carbon backbone, which display many types of modifications in nature. The diversity of natural Sia presentations is magnified by a variety of glycosidic linkages to underlying glycans, the sequences and classes of such glycans, as well as the spatial organization of Sias with their surroundings. This diversity is closely linked to the numerous and varied biological functions of Sias. Relatively large libraries of natural and unnatural Sias have recently been chemically/chemoenzymatically synthesized and/or isolated from natural sources. The resulting sialoglycan microarrays have proved to be valuable tools for the exploration of diversity and biology of Sias. Here we provide an overview of Sia diversity in nature, the approaches used to generate sialoglycan microarrays, and the achievements and challenges arising.

A major obstacle to clinical applications of xenotransplantation is the expression of immunogenic xenoantigens that provide targets for immune recognition of xenografts, leading to activation of host immunity and consequent rejection or poor engraftment. Among the best known xenoantigens is the “αGal” epitope (Galα1−3Galβ1−(3)4GlcNAc-R, where R is an underlying glycoconjugate) characterized by Galili and colleagues. This epitope is widely expressed by most mammals other than old world primates and recognized by abundant circulating human anti-α-Gal antibodies (1). Such antibodies are universally induced after birth in humans via exposure to gut bacteria bearing similar epitopes (2), and the resulting difficulties in xenotransplantation (3) have even encouraged production of alpha1,3-galactosyltransferase gene-knockout pigs (4) as a potential solution.

The 11q terminal deletion disorder (11q-) is a rare chromosomal disorder caused by a deletion in distal 11q. Fifty-six percent of patients have clinically significant congenital heart defects. A cardiac "critical region" has been identified in distal 11q that contains over 40 annotated genes. In this study, we identify the distal breakpoint of a patient with a paracentric inversion in distal 11q who had hypoplastic left heart and congenital thrombocytopenia. The distal breakpoint mapped to JAM-3, a gene previously identified as a candidate gene for causing HLHS in 11q-. To determine the role of JAM-3 in cardiac development, we performed a comprehensive cardiac phenotypic assessment in which the mouse homolog for JAM-3, JAM-C, has been deleted. These mice have normal cardiac structure and function, indicating that haplo-insufficiency of JAM-3 is unlikely to cause the congenital heart defects that occur in 11q- patients. Notably, we identified a previously undescribed phenotype, jitteriness, in most of the sick or dying adult JAM-C knockout mice. These data provide further insights into the identification of the putative disease-causing cardiac gene(s) in distal 11q, as well as the functions of JAM-C in normal organ development.

Sialic acids are monosaccharides with a 9-carbon backbone and are terminating units of glycoconjugates that coat the vertebrate cell surface. The two major types are N-acetylneuraminic acid (Neu5Ac...

Immune receptors that show high mutual sequence similarity and have antagonizing signaling properties are called paired receptors, and are believed to fine-tune immune responses. Siglecs are sialic acid-recognizing receptors of the immunoglobulin (Ig) superfamily expressed on immune cells. Human Siglec-5, encoded by SIGLEC5 gene, has four extracellular Ig-like domains and a cytosolic inhibitory motif. We discovered human Siglec-14 with three Ig-like domains, encoded by the SIGLEC14 gene, adjacent to SIGLEC5. Human Siglec-14 has almost complete sequence identity with human Siglec-5 at the first two Ig-like domains, shows a glycan binding preference similar to that of human Siglec-5, and associates with the activating adapter protein DAP12. Thus, Siglec-14 and Siglec-5 appear to be the first glycan binding paired receptors. Near-complete sequence identity of the amino-terminal part of human Siglec-14 and Siglec-5 indicates partial gene conversion between SIGLEC14 and SIGLEC5. Remarkably, SIGLEC14 and SIGLEC5 in other primates also show evidence of gene conversions within each lineage. Evidently, balancing the interactions between Siglec-14, Siglec-5 and their common ligand(s) had selective advantage during the course of evolution. The "essential arginine" critical for sialic acid recognition in both Siglec-14 and Siglec-5 is present in humans but mutated in almost all great ape alleles.

Metabolism of the major mammalian sialic acid N-glycolylneuraminic acid (Neu5Gc) generates N-glycolylglucosamine (GlcNGc) as a byproduct of its degradative pathway (1). Mammalian cells cultured wit...

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.

The sialic acids are acidic monosaccharides typically found at the outermost ends of the sugar chains of animal glycoconjugates. They potentially can inhibit intermolecular and intercellular interactions by virtue of their negative charge. However, they can also act as critical components of ligands recognized by a variety of proteins of animal, plant, and microbial origin (sialic acid binding lectins). Recognition can be affected by specific structural variations and modifications of sialic acids, their linkage to the underlying sugar chain, the structure of these chains, and the nature of the glycoconjugate to which they are attached. Presented here is a summary of the various proteins that can recognize and bind to this family of monosaccharides, comparing and contrasting the structural requirements and mechanisms involved in binding. Particular attention is focused on the recently evolving information about sialic acid recognition by certain C-type lectins (the selectins), I-type lectins (e.g., CD22 and sialoadhesin), and a complement regulatory protein (the H protein). The last two instances are examples of the importance of the side chain of sialic acids and the effects of natural substitutions (e.g., 9-O-acetylation) of this part of the molecule.