Edwin A. Azen

A primary genetic linkage map for human chromosome 12.

A primary genetic map for human chromosome 12 has been constructed from data on 23 restriction fragment length polymorphic systems collected in 38 normal families with large sibships. Linkage analysis of the genotypic data has ordered 16 loci into a continuous genetic map of 111 cM in males and 258 cM in females. Although most of the genetic map reflects a higher rate of recombination in females relative to males, significantly more frequent recombination was observed in males than in females in intervals between loci on the distal portion of the short arm of the chromosome. The mapping data shown here will serve as a first step toward a high-resolution genetic map for human chromosome 12.

Genetic Polymorphism of Proline-Rich Human Salivary Proteins

In randomly collected saliva samples from 120 Caucasians, 79 Blacks, and 40 Chinese, three phenotypes were observed by electrophoresis in alkaline slab polyacrylamide gels. The proteins showing polymorphism were identical with four previously characterized proline-rich proteins. Inheritance is controlled by two autosomal codominant alleles. The gene frequencies were for Caucasians, Prl=0.73, Pr2=0.27; for Blacks, Pr1=0.80, Pr2=0.20; for Chinese, Prl=0.84, Pr2=0.16.

Histatins, a family of salivary histidine-rich proteins, are encoded by at least two loci (HIS1 and HIS2)

We screened a human parotid gland cDNA library with mixed synthetic oligonucleotide probes representing a central coding region common to histatins 1 and 3. Sequence analysis of 12 histatin cDNA clones strongly suggests that the histatin protein family is encoded by at least two closely related loci (HIS1 and HIS2) such that histatins 1 and 3 are primary products of HIS1(1) and HIS2(1) alleles, respectively, and that histatins 4-6 are derived from histatin 3 by proteolysis. We present additional data indicating that histatin 2 may represent the non-phosphorylated form of histatin 1.

Genetic Polymorphism of C'3(β1c-Globuiin) in Human Serum

Genetic polymorphism of the third component of human complement and its breakdown products has been detected in human serum by high-voltage starch-gel electrophoresis. Six phenotypes were observed in a study of 113 randomly chosen Caucasians. Their inheritance is controlled by four codominant alleles at an autosomal locus. The gene frequencies in this study were C31, 0.21; C32, 0.77; C33, ∼0.01; and C34, ∼0.004.

Tissue Distribution of RNAs for Cystatins, Histatins, Statherin, and Proline-rich Salivary Proteins in Humans and Macaques

The tissue distribution of the mRNAs for a number of salivary proteins [proline-rich proteins (PRPs), statherin, cystatins, and the histatins] has been examined in humans and macaques in order to investigate their possible functions and tissue-specific regulation. We have shown that PRP RNAs (0.8-1.5 kb) are expressed in human and rhesus parotid and submandibular glands, and in the human bronchus. The genes for the acidic and basic PRPs are differentially regulated in these tissues. RNAs for acidic PRPs are predominantly expressed in the submandibular gland, for basic PRPs in the respiratory tract, and for both acidic and basic PRPs in the parotid gland. Protein studies of secretions from these tissues confirm the RNA results. Statherin RNA (0.65 kb) was detected in human and rhesus parotid and submandibular glands and the human bronchus, as well as in rhesus lacrimal glands. Statherin was found by tissue immunoperoxidase staining in the serous cells of respiratory tract submucosal glands, which is the same location for the synthesis of PRPs. Several cystatin RNAs (0.8-1.3 kb) were differentially expressed in human parotid glands, submandibular glands, and the bronchus, and in lacrimal glands from both rhesus and cynomolgus macaques. RNAs (0.6 kb) for the histatins were found only in parotid and submandibular glands. Thus, it appears that PRPs, statherin, and cystatins may play a broader role in the physiology of biological fluids and secretions than previously suspected, since they are found in secretions other than saliva. However, the functions of the histatins are restricted to saliva. These studies also pose some interesting questions regarding the differential expression of these genes in a variety of secretory tissues.

Chromosome mapping ofSoa, a gene influencing gustatory sensitivity to sucrose octaacetate in mice

Strain distribution patterns among recombinant inbred strains suggested that a locus influencing taste sensitivity to sucrose octaacetate was on chromosome 6. A location forSoa was established by linkage analysis of behavioral and electrophoretic data from outbred and congenic strains and from test-cross progeny. Haplotyping of 41 outbred CFW-Cr animals with a cDNA probe showed perfect cosegregation ofSoa andPrp, a gene for salivary proline-rich proteins. Five of twelve B6. SW-Soaa strains were found to retainLdr-1, lactate dehydrogenase regulator-1, on chromosome 6 as an allelic passenger from the SWR/J donor strain (source of theSoaa Taster allele). Centimorgan distance was estimated using the ABP/Le linkage-testing strain (non-Taster,Soab) and the SWR/J strain (Taster,Soaa) in a testcross breeding system. The data are consistent with a position for theSoa locus on mouse chromosome 6, 62 cM from the centromere.

Genetic Polymorphism of Human Salivary Proline- Rich Proteins: Further Genetic Analysis

Electrophoresis of concentrated parotid saliva on slab polyacrylamide gels negatively stained with 3,3′-dimethoxybenzidine and hydrogen peroxide (DMB stain) showed nine phenotypes among the proline-rich proteins. These phenotypes are the expression of four autosomal codominant alleles. Gene frequencies are, for Caucasians, Pr1=0.640, Pr1′=0.005, Pr2=0.080, Pr2′=0.275; for Negroes, Pr1=0.700, Pr1′=0.050, Pr2=0.080, Pr2′=0.170; for Chinese, Pr1=0.770, Pr1′=0, Pr2=0, Pr2′=0.230. The presence or absence of another pair of proteins giving the same negative staining is inherited as an autosomal dominant trait (Db). Homozygous Db + + and heterozygous Db + − individuals could not be distinguished. The genetic determinant (Db) for this pair of proteins is either closely linked to or part of the Pr locus. Gene frequencies are, for Caucasians, Db+=0.12, Db−=0.88; for Negroes, Db+=0.56, Db−=0.44; for Chinese, Db+=0.07, Db−=0.93.

Genetics of salivary protein polymorphisms

Human salivary PRPs are determined by six closely linked genes on chromosome 12p13.2. The many PRPs show complex electrophoretic patterns that differ between individuals and reflect numerous genetic polymorphisms. Frequent length and null polymorphisms are common among PRPs. Common themes emerge as a background for these PRP polymorphisms. First, posttranslational proteolysis occurs with double-banded patterns among acidic PRPs and the generation of numerous basic PRPs derived from precursor proteins. Specific mutations may interfere with proteolysis, preventing generation of double-banded acidic PRPs (as with the Pa protein) or of small basic PRPs from precursor proteins (as with Pm proteins). Second, single cysteine substitutions in PRPs (Pa from PRH1 and G1 8 from PRB3) may lead to disulfide bonded homodimers as well as heterodimers with salivary peroxidase. Third, frequent homologous and unequal crossing-over within the PRP gene cluster leads to frequent protein size-variants (intragenic events as with the G1 protein variants) and the generation of the PRB2/1 fusion gene (intergenic event) with deletion of the PRB1 coding region and absence of multiple PRB1 coded proteins (Ps, Pm, Pe) in PRB2/1 homozygotes. Fourth, null mutations may also be produced (as with PsO and G1 0) by single nucleotide changes.

Genetic Polymorphism of Basic Proteins from Parotid Saliva

In a study of 90 randomly chosen parotid salivas from Blacks three phenotypes were observed during acid-urea starch-gel electrophoresis. Inheritance was controlled by two codominant alleles at an autosomal locus. Of 101 Caucasians, one had a heterozygous phenotype indistinguishable electrophoretically from that in Blacks. Gene frequencies were: for Blacks, parotid basic protein (Pbl) = 0.84, (Pb2) = 0.16; for Caucasians, (Pbl) ~ 0.995, (Pb2) ~ 0.005.

Genetic protein polymrophisms in human saliva: An interpretive review

The purpose of this review is to summarize recent progress in the field of genetic protein polymorphisms found in human saliva since 1972. Prior to 1972 most of the investigations were related to amylase. The genetics of salivary amylase will not be considered here, since it has recently been thoroughly reviewed elsewhere (Merritt and Karn, 1977). In this review, special attention will be devoted to the complex interrelationships of the proline-rich (Pr), double-band (Db), acidic protein (Pa), and peroxidase (SAPX) systems. The biochemically related Pr, Db, and Pa systems show distinctive genetic patterns, and there are associations between the phenotypes indicating linkage relationships. There is also evidence for probable interaction of products of the Pa and SAPX loci. Electrophoretic properties of these proteins can be defined in several gel systems, permitting an accurate definition of phenotypes. The usefulness and limitations of the different gel systems in the interpretation of these electrophoretic patterns will be illustrated. Allelic frequencies of the systems to be discussed are given in Table I. To aid comprehension, the systems will be discussed in logical rather than historical sequence.