Atg7 Knockdown Reduces Chemerin Secretion in Murine Adipocytes

CONTEXT

In individuals with obesity, adipocyte endocrine function is affected by altered autophagy. Genetic variants in autophagy-related gene 7 (ATG7) correlated with serum chemerin (RARRES2) concentrations.

OBJECTIVES

To investigate a functional interplay between chemerin and ATG7, how it may relate to autophagy-mediated adipocyte dysfunction in obesity, and the relevance of genetic ATG7 variants in chemerin physiology.

DESIGN

Adipose ATG7 mRNA expression and adiposity measures were available in two human study cohorts. The effect of a high-calorie diet on adipose Rarres2 and Atg7 expression was investigated in mice. In 3T3-L1 adipocytes, the effect of Atg7 knockdown on chemerin expression and secretion was studied. The influence of single nucleotide polymorphisms on ATG7 transcription and chemerin physiology was investigated using a luciferase assay.

SETTING

Mouse model, clinical trials, in vitro studies.

PARTICIPANTS

Native American (n = 83) and white (n = 100) cohorts.

MAIN OUTCOME MEASURE

Adipocyte chemerin expression and secretion.

RESULTS

In mice fed a high-calorie diet, adipose Atg7 mRNA expression did not parallel an increase in Rarres2 mRNA expression. ATG7 mRNA expression in human subcutaneous adipose tissue correlated with body mass index, fat mass (r > 0.27; P < 0.01), and adipocyte cell size (r > 0.24; P < 0.02). Atg7 knockdown in 3T3-L1 adipocytes decreased chemerin secretion by 22% (P < 0.04). Rs2606729 in ATG7 was predicted to alter ATG7 transcription and induced higher luciferase activity in vitro (P < 0.0001).

CONCLUSIONS

Human adipose ATG7 mRNA expression relates to measures of adiposity. Atg7 knockdown reduces chemerin secretion from adipocytes in vitro, supportive of a functional interplay between ATG7 and chemerin in autophagy-mediated adipocyte dysfunction.

Safety of Direct-Acting Antiviral Therapy Regarding Renal Function in Post-Liver Transplant Patients Infected with Hepatitis C Virus and a 100% 12-Week Sustained Virologic Response-A Single-Center Study

BACKGROUND

Patients after liver transplantation (LT) with hepatitis C virus (HCV) infection often suffer from renal or hepatic impairment. Treating patients after LT with direct-acting antivirals (DAA) might result in decreasing renal function due to interaction of DAA and immunosuppressive therapy. In this single-center study we analyzed clinical parameters of 18 HCV-infected patients treated with DAA therapy after LT.

METHODS

The primary end points were change of renal function (glomerular filtration rate) and sustained virologic response 12 weeks after therapy (SVR12). For secondary end points, we investigated the influence of DAA therapy on transaminases, bilirubin, international normalized ratio, noninvasive fibrosis measurement, and Model for End-Stage Liver Disease (MELD) score.

RESULTS

Five out of 18 patients treated with DAA suffered from renal impairment stage 2, and 7 patients of renal impairment stage 3. Renal function at SVR12 was not influenced by preexisting renal impairment (P > .5), type of immunosuppressant (P > .5), or type of DAA regimen (P > .5). All patients reached SVR12. The levels of transaminases and bilirubin declined rapidly, as expected. Ten out of 18 patients already suffered from cirrhosis or liver fibrosis >F3 according to noninvasive measurement before initiation of treatment. Single-point acoustic radiation force impulse imaging improved in 9 patients (P = .012). In 7 patients, MELD score improved owing to the decrease of bilirubin levels. In 6 patients it worsened.

CONCLUSIONS

DAA therapy in LT patients was effective and safe in this single-center real-life cohort. Renal function was not influenced by the administered drug combinations, even in patients with preexisting renal impairment.

A Genome-Wide Association Study of IVGTT-Based Measures of First-Phase Insulin Secretion Refines the Underlying Physiology of Type 2 Diabetes Variants

Understanding the physiological mechanisms by which common variants predispose to type 2 diabetes requires large studies with detailed measures of insulin secretion and sensitivity. Here we performed the largest genome-wide association study of first-phase insulin secretion, as measured by intravenous glucose tolerance tests, using up to 5,567 individuals without diabetes from 10 studies. We aimed to refine the mechanisms of 178 known associations between common variants and glycemic traits and identify new loci. Thirty type 2 diabetes or fasting glucose-raising alleles were associated with a measure of first-phase insulin secretion at P < 0.05 and provided new evidence, or the strongest evidence yet, that insulin secretion, intrinsic to the islet cells, is a key mechanism underlying the associations at the HNF1A, IGF2BP2, KCNQ1, HNF1B, VPS13C/C2CD4A, FAF1, PTPRD, AP3S2, KCNK16, MAEA, LPP, WFS1, and TMPRSS6 loci. The fasting glucose-raising allele near PDX1, a known key insulin transcription factor, was strongly associated with lower first-phase insulin secretion but has no evidence for an effect on type 2 diabetes risk. The diabetes risk allele at TCF7L2 was associated with a stronger effect on peak insulin response than on C-peptide-based insulin secretion rate, suggesting a possible additional role in hepatic insulin clearance or insulin processing. In summary, our study provides further insight into the mechanisms by which common genetic variation influences type 2 diabetes risk and glycemic traits.

Genome-wide Association Study of Platelet Count Identifies Ancestry-Specific Loci in Hispanic/Latino Americans

Platelets play an essential role in hemostasis and thrombosis. We performed a genome-wide association study of platelet count in 12,491 participants of the Hispanic Community Health Study/Study of Latinos by using a mixed-model method that accounts for admixture and family relationships. We discovered and replicated associations with five genes (ACTN1, ETV7, GABBR1-MOG, MEF2C, and ZBTB9-BAK1). Our strongest association was with Amerindian-specific variant rs117672662 (p value = 1.16 × 10(-28)) in ACTN1, a gene implicated in congenital macrothrombocytopenia. rs117672662 exhibited allelic differences in transcriptional activity and protein binding in hematopoietic cells. Our results underscore the value of diverse populations to extend insights into the allelic architecture of complex traits.

Hyperphagia: current concepts and future directions proceedings of the 2nd international conference on hyperphagia

OBJECTIVE

Hyperphagia is a central feature of inherited disorders (e.g., Prader-Willi Syndrome) in which obesity is a primary phenotypic component. Hyperphagia may also contribute to obesity as observed in the general population, thus raising the potential importance of common underlying mechanisms and treatments. Substantial gaps in understanding the molecular basis of inherited hyperphagia syndromes are present as are a lack of mechanistic of mechanistic targets that can serve as a basis for pharmacologic and behavioral treatments.

DESIGN AND METHODS

International conference with 28 experts, including scientists and caregivers, providing presentations, panel discussions, and debates.

RESULTS

The reviewed collective research and clinical experience provides a critical body of new and novel information on hyperphagia at levels ranging from molecular to population. Gaps in understanding and tools needed for additional research were identified.

CONCLUSIONS

This report documents the full scope of important topics reviewed at a comprehensive international meeting devoted to the topic of hyperphagia and identifies key areas for future funding and research.

NGSPE: A pipeline for end-to-end analysis of DNA sequencing data and comparison between different platforms

We present NGSPE, a pipeline for variation discovery and genotyping of pair-ended Illumina next generation sequencing (NGS) data (http://ngspeanalysis.sourceforge.net/). This pipeline not only describes a set of sequential analytical steps, such as short reads alignment, genotype calling and functional variation annotation that can be conducted using open-source software tools, but also provides users a set of scripts to install the dependent software and resources and implement the pipeline on their data. A sample summary report including the concordance rate between data generated by this pipeline and different resources as well as the comparison between replication samples of two commercial platforms from Illumina and Complete Genomics is also provided. Furthermore, some of the mutations identified by the pipeline were verified using Sanger sequencing.

Involvement of the chemokine-like receptor GPR33 in innate immunity

Chemokine receptors control leukocyte chemotaxis and cell-cell communication but have also been associated with pathogen entry. GPR33, an orphan member of the chemokine-like receptor family, is a pseudogene in most humans. After the appearance of GPR33 in first mammalian genomes, this receptor underwent independent pseudogenization in humans, other hominoids and some rodent species. It was speculated that a likely cause of GPR33 inactivation was its interplay with a rodent-hominoid-specific pathogen. Simultaneous pseudogenization in several unrelated species within the last 1 million years (myr) caused by neutral drift appears to be very unlikely suggesting selection on the GPR33 null-allele. Although there are no signatures of recent selection on human GPR33 we found a significant increase in the pseudogene allele frequency in European populations when compared with African and Asian populations. Because its role in the immune system was still hypothetical expression analysis revealed that GPR33 is highly expressed in dendritic cells (DC). Murine GPR33 expression is regulated by the activity of toll-like receptors (TLR) and AP-1/NF-kappaB signaling pathways in cell culture and in vivo. Our data indicate an important role of GPR33 function in innate immunity which became dispensable during human evolution most likely due to past or balancing selection.

Linkage disequilibrium mapping of the replicated type 2 diabetes linkage signal on chromosome 1q

OBJECTIVE

Linkage of the chromosome 1q21-25 region to type 2 diabetes has been demonstrated in multiple ethnic groups. We performed common variant fine-mapping across a 23-Mb interval in a multiethnic sample to search for variants responsible for this linkage signal.

RESEARCH DESIGN AND METHODS

In all, 5,290 single nucleotide polymorphisms (SNPs) were successfully genotyped in 3,179 type 2 diabetes case and control subjects from eight populations with evidence of 1q linkage. Samples were ascertained using strategies designed to enhance power to detect variants causal for 1q linkage. After imputation, we estimate approximately 80% coverage of common variation across the region (r (2) > 0.8, Europeans). Association signals of interest were evaluated through in silico replication and de novo genotyping in approximately 8,500 case subjects and 12,400 control subjects.

RESULTS

Association mapping of the 23-Mb region identified two strong signals, both of which were restricted to the subset of European-descent samples. The first mapped to the NOS1AP (CAPON) gene region (lead SNP: rs7538490, odds ratio 1.38 [95% CI 1.21-1.57], P = 1.4 x 10(-6), in 999 case subjects and 1,190 control subjects); the second mapped within an extensive region of linkage disequilibrium that includes the ASH1L and PKLR genes (lead SNP: rs11264371, odds ratio 1.48 [1.18-1.76], P = 1.0 x 10(-5), under a dominant model). However, there was no evidence for association at either signal on replication, and, across all data (>24,000 subjects), there was no indication that these variants were causally related to type 2 diabetes status.

CONCLUSIONS

Detailed fine-mapping of the 23-Mb region of replicated linkage has failed to identify common variant signals contributing to the observed signal. Future studies should focus on identification of causal alleles of lower frequency and higher penetrance.

A Gly482Ser missense mutation in the peroxisome proliferator-activated receptor gamma coactivator-1 is associated with altered lipid oxidation and early insulin secretion in Pima Indians

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) is a transcriptional coactivator of peroxisome proliferator-activated receptor gamma and alpha, which play important roles in adipogenesis and lipid metabolism. A single nucleotide polymorphism within the coding region of the PGC-1 gene predicts a glycine to serine substitution at amino acid 482 and has been associated with type 2 diabetes in a Danish population. In this study, we examined whether this Gly482Ser polymorphism is associated with type 2 diabetes or obesity, or metabolic predictors of these diseases, in Pima Indians. There was no association of the Gly482Ser polymorphism with either type 2 diabetes or BMI (n = 984). However, among nondiabetic Pima Indians (n = 183-201), those with the Gly/Gly genotype had a lower mean insulin secretory response to intravenous and oral glucose and a lower mean rate of lipid oxidation (over 24 h in a respiratory chamber) despite a larger mean subcutaneous abdominal adipocyte size and a higher mean plasma free fatty acid concentration. These data indicate that the Gly482Ser missense polymorphism in PGC-1 has metabolic consequences on lipid metabolism that could influence insulin secretion.

Identification of susceptibility genes for complex metabolic diseases

There are few successful attempts to identify genes for common, non-Mendelian diseases such as diabetes, hyperlipidemia, hypertension, etc. Such common disorders are typically both metabolically and genetically complex and the genetic technologies to identify their underlying susceptibility genes are still in their infancy. Nonetheless, genetic strategies have emerged that, when the technologies are fully developed, should allow similar success rates as for Mendelian diseases.

Positional cloning of an obesity/diabetes susceptibility gene(s) on chromosome 11 in Pima Indians

Prior results from our genomic scan in Pima Indians indicated an obesity locus in a region on chromosome 11q23-24 that was also linked to diabetes. Bivariate linkage analysis for the combined phenotype "diabesity" gave the strongest evidence for linkage (LOD = 5.2). Our aim is to positionally clone the gene(s) responsible for the linkage. Linkage disequilibrium mapping is being used to narrow the chromosomal region. Single nucleotide polymorphisms (SNPs) are being systematically identified and genotyped at 50-kb intervals across the region of linkage. To date, 455 SNPs have been genotyped in 1229 Pimas. A region containing a cluster of SNPs strongly associated with BMI and a second region, approximately 2 Mb telomeric, containing a cluster of SNPs associated with diabetes have been preliminarily identified.

A Ser311Cys mutation in the human dopamine receptor D2 gene is associated with reduced energy expenditure

Brain dopaminergic pathways play a major role in the control of movement. Absence of the murine dopamine D2 receptor gene (drd2) produces bradykinesia and hypothermia. A Ser311Cys mutation of the human DRD2 produces a marked functional impairment of the receptor and is associated with higher BMI in some populations. We hypothesized that the Ser311Cys mutation of DRD2 may inhibit energy expenditure. Here we report that total energy expenditure (doubly labeled water) measured in 89 nondiabetic Pima Indians was 244 kcal/ day lower in homozygotes for the Cys311-encoding allele when compared with those heterozygous and homozygous for the Ser311-encoding allele (P = 0.056). The 24-h resting energy expenditure (respiratory chamber) measured in 320 nondiabetic Pimas was also 87 kcal/day lower in homozygotes for the Cys311-encoding allele when compared with those heterozygous and homozygous for the Ser311-encoding allele (P = 0.026). These findings are the first evidence that a genetic mutation is associated with reduced energy expenditure in humans. Because the impact of this mutation on human obesity is small, we suggest that either the energy deficit induced is not large enough to significantly influence body weight in this population and/or that the Cys311-encoding allele is also associated with reduced energy intake.

Effects of an Ala54Thr polymorphism in the intestinal fatty acid-binding protein on responses to dietary fat in humans

A polymorphism in FABP2 that results in an alanine-to-threonine substitution at amino acid 54 of the intestinal fatty acid-binding protein (IFABP) is associated with insulin resistance in Pima Indians. In vitro, the threonine form (Thr54) has a higher binding affinity for long-chain fatty acids than does the alanine form (Ala54). We tested whether this polymorphism affected metabolic responses to dietary fat, in vivo. Eighteen healthy Pima Indians, half homozygous for the Thr54 form of IFABP and half homozygous for the Ala54 form, were studied. The groups were matched for sex, age, and body mass index. Plasma triglyceride, nonesterified fatty acid (NEFA), glucose, and insulin responses were measured after a mixed meal (35% of daily energy requirements, 50 g of fat) and after a high fat challenge (1362 kcal, 129 g of fat). NEFA concentrations were approximately 15% higher after the mixed meal and peaked earlier and were approximately 20% higher at 7 h in response to the high fat test meal in Thr54 homozygotes compared with Ala54 homozygotes. Insulin responses to the test meals tended to be higher in Thr54 homozygotes, but glucose and triglyceride responses were not different.The results of this study suggest that the Thr54 form of IFABP is associated with higher and prolonged NEFA responses to dietary fat in vivo. Higher NEFA concentrations may contribute to insulin resistance and hyperinsulinemia in individuals with this allele.

Association of dopamine D2 receptor polymorphisms Ser311Cys and TaqIA with obesity or type 2 diabetes mellitus in Pima Indians

OBJECTIVES

To investigate whether (a) variants within the dopamine D2 receptor gene (DRD2) are associated with obesity and type 2 diabetes in Pima Indians, and (b) whether variation in this gene could be responsible for previously observed linkage to these phenotypes, at chromosome location 11q23-24, in this population.

DESIGN

Two single nucleotide polymorphisms (SNPs), Ser311Cys and TaqIA, within the DRD2 gene were genotyped by allelic discrimination PCR in subjects who had provided evidence of linkage to diabetes and obesity in an autosome-wide scan.

SUBJECTS

A total of 1,187 subjects were genotyped, including 947 full heritage Pima Indians (80%). Descriptive statistics for all subjects analyzed, for whom clinical data were available, were (mean+/-s.d.): age at time of last exam = 41 +/- 15 y; birth year=1950 +/- 14; age-sex-adjusted body mass index (BMI; adjusted to a mean age of 35y)=36 +/- 8kg/m2; male = 44%; diabetic = 57%. For full heritage Pimas only: age = 43 +/- 15 y; birth year = 1948 +/- 14; sex- age-adjusted BMI = 36 +/- 8 kg/m2; male = 43%; diabetic = 59%.

RESULTS

Neither polymorphism was significantly associated with diabetes in full heritage Pimas. Individuals with a 'CG' genotype at the Ser311Cys SNP had a higher BMI than those with a 'CC' genotype (36.7 vs 35.5 kg/m2, P= 0.04). Linkage analysis of BMI, adjusted for either polymorphism, resulted in LOD scores that were similar to those obtained without adjustment.

CONCLUSION

Heterozygotes at the Ser311Cys DRD2 polymorphism had a slightly higher BMI than homozygotes, however neither the Ser311Cys nor the TaqIA polymorphism accounted for the linkage with BMI on chromosome 11 in Pima Indians.

An autosomal genomic scan for loci linked to type II diabetes mellitus and body-mass index in Pima Indians

Genetic factors influence the development of type II diabetes mellitus, but genetic loci for the most common forms of diabetes have not been identified. A genomic scan was conducted to identify loci linked to diabetes and body-mass index (BMI) in Pima Indians, a Native American population with a high prevalence of type II diabetes. Among 264 nuclear families containing 966 siblings, 516 autosomal markers with a median distance between adjacent markers of 6.4 cM were genotyped. Variance-components methods were used to test for linkage with an age-adjusted diabetes score and with BMI. In multipoint analyses, the strongest evidence for linkage with age-adjusted diabetes (LOD = 1.7) was on chromosome 11q, in the region that was also linked most strongly with BMI (LOD = 3.6). Bivariate linkage analyses strongly rejected both the null hypothesis of no linkage with either trait and the null hypothesis of no contribution of the locus to the covariation among the two traits. Sib-pair analyses suggest additional potential diabetes-susceptibility loci on chromosomes 1q and 7q.

An autosomal genomic scan for loci linked to prediabetic phenotypes in Pima Indians

Type 2 diabetes mellitus is a common chronic disease that is thought to have a substantial genetic basis. Identification of the genes responsible has been hampered by the complex nature of the syndrome. Abnormalities in insulin secretion and insulin action predict the development of type 2 diabetes and are, themselves, highly heritable traits. Since fewer genes may contribute to these precursors of type 2 diabetes than to the overall syndrome, such genes may be easier to identify. We, therefore, undertook an autosomal genomic scan to identify loci linked to prediabetic traits in Pima Indians, a population with a high prevalence of type 2 diabetes. 363 nondiabetic Pima Indians were genotyped at 516 polymorphic microsatellite markers on all 22 autosomes. Linkage analyses were performed using three methods (single-marker, nonparametric multipoint [MAPMAKER/SIBS], and variance components multipoint). These analyses provided evidence for linkage at several chromosomal regions, including 3q21-24 linked to fasting plasma insulin concentration and in vivo insulin action, 4p15-q12 linked to fasting plasma insulin concentration, 9q21 linked to 2-h insulin concentration during oral glucose tolerance testing, and 22q12-13 linked to fasting plasma glucose concentration. These results suggest loci that may harbor genes contributing to type 2 diabetes in Pima Indians. None of the linkages exceeded a LOD score of 3.6 (a 5% probability of occurring in a genome-wide scan). These findings must, therefore, be considered tentative until extended in this population or replicated in others.

Autosomal genomic scan for loci linked to obesity and energy metabolism in Pima Indians

An autosomal genomic scan to search for linkage to obesity and energy metabolism was completed in Pima Indians, a population prone to obesity. Obesity was assessed by percent body fat (by hydrodensitometry) and fat distribution (the ratio of waist circumference to thigh circumference). Energy metabolism was measured in a respiratory chamber as 24-h metabolic rate, sleeping metabolic rate, and 24-h respiratory quotient (24RQ), an indicator of the ratio of carbohydrate oxidation to fat oxidation. Five hundred sixteen microsatellite markers with a median spacing of 6.4 cM were analyzed, in 362 siblings who had measurements of body composition and in 220 siblings who had measurements of energy metabolism. These comprised 451 sib pairs in 127 nuclear families, for linkage analysis to obesity, and 236 sib pairs in 82 nuclear families, for linkage analysis to energy metabolism. Pointwise and multipoint methods for regression of sib-pair differences in identity by descent, as well as a sibling-based variance-components method, were used to detect linkage. LOD scores >=2 were found at 11q21-q22, for percent body fat (LOD=2.1; P=.001), at 11q23-q24, for 24-h energy expenditure (LOD=2.0; P=.001), and at 1p31-p21 (LOD=2.0) and 20q11.2 (LOD=3.0; P=.0001), for 24RQ, by pointwise and multipoint analyses. With the variance-components method, the highest LOD score (LOD=2.3 P=.0006) was found at 18q21, for percent body fat, and at 1p31-p21 (LOD=2.8; P=.0003), for 24RQ. Possible candidate genes include LEPR (leptin receptor), at 1p31, and ASIP (agouti-signaling protein), at 20q11.2.

Generic nursing outcome objectives for use in long-term care facilities

Twenty-two registered nurses employed in four long-term care facilities generated data for a study about nursing diagnoses in long-term care (N = 360). Generic outcome objectives were developed as an integral part of the project. The research team also specified exceptions to the outcomes: instances where meeting outcome objectives might not be possible. The outcome objectives and exceptions for the sample's 20 most frequently occurring nursing diagnoses are presented as working statements. The authors expect that these outcome objectives and exceptions will be revised by nurses who use them in practice, basic and continuing education, and research.

Exploratory research as andragogic continuing education

The continuing education aspect of an exploratory research project was evaluated in terms of Knowles's learning assumptions and teaching design factors. Although most of the project's assumptions were congruent with Knowles's andragogic assumptions, the design factors were found to be more pedagogic. Using more andragogic design factors in the future would strengthen this continuing education approach.

Expression of a novel nuclear protein in activated and in tat-I expressing T cells

The intracellular events that occur in T lymphoid cells after activation or after infection with HIV-1 are not well defined. In the case of HIV-1 infection, it is unknown whether the tat-I gene, an essential gene for viral replication, affects host cell nuclear factors. Using two-dimensional PAGE, we have identified a novel nuclear protein, designated nuclear protein-28,000 (NP-28), which is induced in Jurkat T cells by stimulation with PMA and/or PHA or ionomycin. This nuclear protein has an apparent molecular mass of 28,000 Da and an isoelectric point of 4.6. Interestingly, Jurkat cells transfected with tat-I express higher levels of NP-28 constitutively, without added stimulation. Incubation of Jurkat cells expressing tat-I with PMA and/or PHA or ionomycin causes superinduction of NP-28. We have therefore identified a novel lymphoid nuclear protein induced by T cell activation that occurs in tat-I expressing cells in the absence of activating agents.

Exploratory project for development of nursing outcome criteria in long term care

This exploratory project in developing outcome criteria for long term care was conducted with the view that the individual professional nursing practitioner has a unique, valuable contribution to make to the overall nursing quality assurance effort. Twenty-seven nurses volunteered to design and conduct individual systematic nursing diagnosis/intervention/outcome measurement projects. They were employees of five long term care facilities in New York state. Their contribution to this project was an embodiment of their professional judgement and practice with 107 selected clients under their care. They were prepared for participation through instruction repeated in all five facilities. The North American Nursing Diagnosis Association's Taxonomy of Nursing Diagnoses was used in the instruction, by the practitioners in their practice and data collection, and in the data analysis. Data analysis also included use of Campbell's nursing intervention category scheme. This work demonstrated that professional nurses are able to specify appropriate outcome criteria and to measure these outcomes of their planned nursing interventions. Eighty-seven percent of the expected outcomes were achieved as anticipated or in the anticipated direction. Results provided many leads for future study of nursing diagnosis/intervention/outcome measurement among residents of long term care institutions.

Frequency of polymorphisms for alleles encoding for liver proteins of domesticated mice

Three different inbred strains of mice have been crossed with a lethal albino line (cch/c3H) and the liver polypeptides of the parents and offspring examined by two-dimensional polyacrylamide gel electrophoresis for evidences of protein polymorphisms, different alleles of which have gone to fixation in different strains. In the battery of polypeptides considered most favorable for scoring, 3.3 +/- 1.6 percent of the battery exhibited paired variants and 1.6 +/- 1.2 percent, unpaired. An adjustment for the fact the same allele of a biallelic polymorphism may go to fixation in two inbred lines of common ancestry leads to the suggestion that in the stock from which these inbred lines were ultimately derived, there were some 11.0 percent paired and 5.3 percent unpaired polymorphisms in the average mouse. This is about half the frequency of polymorphisms observed in wild European Mus musculus musculus and Mus musculus domesticus with one-dimensional electrophoresis of blood plasma and erythrocyte proteins. Three explanations were considered for the lower estimated frequency for liver protein polymorphisms: the difference is real, the apparent difference is due to the lower resolving power of two-dimensional gels, or the mouse strains from which the present inbred lines were drawn had already, lost through inbreeding, a considerable amount of their genetic variation before the inbreeding leading to the present strains commenced.