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In unrelated individuals, their phenotypes at two gene loci may appear correlated. The two major reasons for such a deviation from independence are linkage disequilibrium (allelic association) and an interaction between the phenotypes. In this paper, it is shown how the usual chi-square test for association of phenotypes can be partitioned into two components, one being due to allelic association and the other being due to other causes of phenotypic association. The test is demonstrated with an example.

Huntington disease (HD) is a late onset autosomal dominant neurological disorder. Two hundred fifty-three death certificates of HD-affected individuals from four midwestern states were examined to determine the completeness of reporting HD on the death certificates. Overall, 66% of death certificates indicated HD as a primary or contributory cause of death. There was significantly better reporting on more recent death certificates, but even since 1979, 16% did not report HD. The implications to those researching HD family histories and to the accuracy of mortality rates are discussed.

Background/Aims: It has been hypothesized that choline acetyltransferase (ChAT) activity might be associated with cognitive impairment in Alzheimer’s disease (AD). A functional single nucleotide polymorphism (2384 G/A) of ChAT was proposed to be associated with AD risk and age of onset. The aim of this study was to evaluate this polymorphism in a cohort of Chinese AD patients and patients with mild cognitive impairment (MCI). Methods: We conducted a case-control study in 273 cases of sporadic AD, 97 MCI patients and 271 nondemented controls from the Chinese Han population. Results: In AD, ChAT 2384 A carriers had a significantly earlier age of onset and worse individual cognitive function in Fuld Object-Memory Evaluation; in MCI, the carriers of both 2384 A and ApoE Ε4 had a significantly earlier age of onset. Conclusion:ChAT 2384 A allele is a risk factor for AD and MCI.

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Background Odor identification (OI) dysfunction is an early marker of Alzheimer’s disease (AD), but it remains unclear how olfactory-related regions change from stages of subjective cognitive decline (SCD) and mild cognitive impairment (MCI) to AD dementia. Methods Two hundred and sixty-nine subjects were recruited in the present study. The olfactory-related regions were defined as the regions of interest, and the grey matter volume (GMV), low-frequency fluctuation (ALFF), regional homogeneity (ReHo) and functional connectivity (FC) were compared to explore the changing pattern of structural and functional abnormalities across AD, MCI, SCD and normal controls. Results From the SCD, MCI to AD groups, the reduced GMV, increased ALFF, increased ReHo and reduced FC of olfactory-related regions became increasingly severe, and only the degree of reduced GMV of hippocampus and caudate nucleus clearly distinguished the 3 groups. In particular, SCD subjects exhibited reduced GMV (hippocampus, etc.), increased ReHo (caudate nucleus) and reduced FC (hippocampus- hippocampus and hippocampus-parahippocampus ) in olfactory-related regions compared with normal controls. Additionally, reduced GMV of the bilateral hippocampus and increased ReHo of the right caudate nucleus were associated with OI dysfunction and global cognitive impairment, and they exhibited partially mediated effects on the relationships between OI and global cognition across all subjects. Conclusion Structural and functional abnormalities of olfactory-related regions present early with SCD and deepen with disease severity in the AD spectrum. The hippocampus and caudate nucleus may be the hub joining OI and cognitive function in the AD spectrum.

Parotid saliva contains a variety of proline-rich proteins. This study found that, among 306 children between the ages of 5 to 15 years, there is a significant increase in the decayed-missing-filled tooth surface (DMFS) score of the permanent teeth with age in children with the specific proline-rich protein phenotypes Pa and Pr. However, the increase in DMFS score of the permanent teeth of children was significantly greater in children with Pa+ and Pr22 than in those with the other phenotypes (Pa- or Pr11 and Pr12). The previously established close correlation between the Pa and Pr phenotypes and the genetic variants of salivary peroxidase (a powerful antibacterial system in the oral cavity) may provide an explanation for the relationship of certain proline-rich protein phenotypes to dental caries.