Precision medicine for suicidality: from universality to subtypes and personalization.

Suicide remains a clear, present and increasing public health problem, despite being a potentially preventable tragedy. Its incidence is particularly high in people with overt or un(der)diagnosed psychiatric disorders. Objective and precise identification of individuals at risk, ways of monitoring response to treatments and novel preventive therapeutics need to be discovered, employed and widely deployed. We sought to investigate whether blood gene expression biomarkers for suicide (that is, a 'liquid biopsy' approach) can be identified that are more universal in nature, working across psychiatric diagnoses and genders, using larger cohorts than in previous studies. Such markers may reflect and/or be a proxy for the core biology of suicide. We were successful in this endeavor, using a comprehensive stepwise approach, leading to a wealth of findings. Steps 1, 2 and 3 were discovery, prioritization and validation for tracking suicidality, resulting in a Top Dozen list of candidate biomarkers comprising the top biomarkers from each step, as well as a larger list of 148 candidate biomarkers that survived Bonferroni correction in the validation step. Step 4 was testing the Top Dozen list and Bonferroni biomarker list for predictive ability for suicidal ideation (SI) and for future hospitalizations for suicidality in independent cohorts, leading to the identification of completely novel predictive biomarkers (such as CLN5 and AK2), as well as reinforcement of ours and others previous findings in the field (such as SLC4A4 and SKA2). Additionally, we examined whether subtypes of suicidality can be identified based on mental state at the time of high SI and identified four potential subtypes: high anxiety, low mood, combined and non-affective (psychotic). Such subtypes may delineate groups of individuals that are more homogenous in terms of suicidality biology and behavior. We also studied a more personalized approach, by psychiatric diagnosis and gender, with a focus on bipolar males, the highest risk group. Such a personalized approach may be more sensitive to gender differences and to the impact of psychiatric co-morbidities and medications. We compared testing the universal biomarkers in everybody versus testing by subtypes versus personalized by gender and diagnosis, and show that the subtype and personalized approaches permit enhanced precision of predictions for different universal biomarkers. In particular, LHFP appears to be a strong predictor for suicidality in males with depression. We also directly examined whether biomarkers discovered using male bipolars only are better predictors in a male bipolar independent cohort than universal biomarkers and show evidence for a possible advantage of personalization. We identified completely novel biomarkers (such as SPTBN1 and C7orf73), and reinforced previously known biomarkers (such as PTEN and SAT1). For diagnostic ability testing purposes, we also examined as predictors phenotypic measures as apps (for suicide risk (CFI-S, Convergent Functional Information for Suicidality) and for anxiety and mood (SASS, Simplified Affective State Scale)) by themselves, as well as in combination with the top biomarkers (the combination being our a priori primary endpoint), to provide context and enhance precision of predictions. We obtained area under the curves of 90% for SI and 77% for future hospitalizations in independent cohorts. Step 5 was to look for mechanistic understanding, starting with examining evidence for the Top Dozen and Bonferroni biomarkers for involvement in other psychiatric and non-psychiatric disorders, as a mechanism for biological predisposition and vulnerability. The biomarkers we identified also provide a window towards understanding the biology of suicide, implicating biological pathways related to neurogenesis, programmed cell death and insulin signaling from the universal biomarkers, as well as mTOR signaling from the male bipolar biomarkers. In particular, HTR2A increase coupled with ARRB1 and GSK3B decreases in expression in suicidality may provide a synergistic mechanistical corrective target, as do SLC4A4 increase coupled with AHCYL1 and AHCYL2 decrease. Step 6 was to move beyond diagnostics and mechanistical risk assessment, towards providing a foundation for personalized therapeutics. Items scored positive in the CFI-S and subtypes identified by SASS in different individuals provide targets for personalized (psycho)therapy. Some individual biomarkers are targets of existing drugs used to treat mood disorders and suicidality (lithium, clozapine and omega-3 fatty acids), providing a means toward pharmacogenomics stratification of patients and monitoring of response to treatment. Such biomarkers merit evaluation in clinical trials. Bioinformatics drug repurposing analyses with the gene expression biosignatures of the Top Dozen and Bonferroni-validated universal biomarkers identified novel potential therapeutics for suicidality, such as ebselen (a lithium mimetic), piracetam (a nootropic), chlorogenic acid (a polyphenol) and metformin (an antidiabetic and possible longevity promoting drug). Finally, based on the totality of our data and of the evidence in the field to date, a convergent functional evidence score prioritizing biomarkers that have all around evidence (track suicidality, predict it, are reflective of biological predisposition and are potential drug targets) brought to the fore APOE and IL6 from among the universal biomarkers, suggesting an inflammatory/accelerated aging component that may be a targetable common denominator.

Orthogonal Comparison of Molecular Signatures of Kidney Transplants With Subclinical and Clinical Acute Rejection: Equivalent Performance Is Agnostic to Both Technology and Platform.

We performed orthogonal technology comparisons of concurrent peripheral blood and biopsy tissue samples from 69 kidney transplant recipients who underwent comprehensive algorithm-driven clinical phenotyping. The sample cohort included patients with normal protocol biopsies and stable transplant (sTx) function (n = 25), subclinical acute rejection (subAR, n = 23), and clinical acute rejection (cAR, n = 21). Comparisons between microarray and RNA sequencing (RNA-seq) signatures were performed and demonstrated a strong correlation between the blood and tissue compartments for both technology platforms. A number of shared differentially expressed genes and pathways between subAR and cAR in both platforms strongly suggest that these two clinical phenotypes form a continuum of alloimmune activation. SubAR is associated with fewer or less expressed genes than cAR in blood, whereas in biopsy tissues, this clinical phenotype demonstrates a more robust molecular signature for both platforms. The discovery work done in this study confirms a clear ability to detect gene expression profiles for sTx, subAR, and cAR in both blood and biopsy tissue, yielding equivalent predictive performance that is agnostic to both technology and platform. Our data also provide strong biological insights into the molecular mechanisms underlying these signatures, underscoring their logistical potential as molecular diagnostics to improve clinical outcomes following kidney transplantation.

Towards understanding and predicting suicidality in women: biomarkers and clinical risk assessment.

Women are under-represented in research on suicidality to date. Although women have a lower rate of suicide completion than men, due in part to the less-violent methods used, they have a higher rate of suicide attempts. Our group has previously identified genomic (blood gene expression biomarkers) and clinical information (apps) predictors for suicidality in men. We now describe pilot studies in women. We used a powerful within-participant discovery approach to identify genes that change in expression between no suicidal ideation (no SI) and high suicidal ideation (high SI) states (n=12 participants out of a cohort of 51 women psychiatric participants followed longitudinally, with diagnoses of bipolar disorder, depression, schizoaffective disorder and schizophrenia). We then used a Convergent Functional Genomics (CFG) approach to prioritize the candidate biomarkers identified in the discovery step by using all the prior evidence in the field. Next, we validated for suicidal behavior the top-ranked biomarkers for SI, in a demographically matched cohort of women suicide completers from the coroner's office (n=6), by assessing which markers were stepwise changed from no SI to high SI to suicide completers. We then tested the 50 biomarkers that survived Bonferroni correction in the validation step, as well as top increased and decreased biomarkers from the discovery and prioritization steps, in a completely independent test cohort of women psychiatric disorder participants for prediction of SI (n=33) and in a future follow-up cohort of psychiatric disorder participants for prediction of psychiatric hospitalizations due to suicidality (n=24). Additionally, we examined how two clinical instruments in the form of apps, Convergent Functional Information for Suicidality (CFI-S) and Simplified Affective State Scale (SASS), previously tested in men, perform in women. The top CFI-S item distinguishing high SI from no SI states was the chronic stress of social isolation. We then showed how the clinical information apps combined with the 50 validated biomarkers into a broad predictor (UP-Suicide), our apriori primary end point, predicts suicidality in women. UP-Suicide had a receiver-operating characteristic (ROC) area under the curve (AUC) of 82% for predicting SI and an AUC of 78% for predicting future hospitalizations for suicidality. Some of the individual components of the UP-Suicide showed even better results. SASS had an AUC of 81% for predicting SI, CFI-S had an AUC of 84% and the combination of the two apps had an AUC of 87%. The top biomarker from our sequential discovery, prioritization and validation steps, BCL2, predicted future hospitalizations due to suicidality with an AUC of 89%, and the panel of 50 validated biomarkers (BioM-50) predicted future hospitalizations due to suicidality with an AUC of 94%. The best overall single blood biomarker for predictions was PIK3C3 with an AUC of 65% for SI and an AUC of 90% for future hospitalizations. Finally, we sought to understand the biology of the biomarkers. BCL2 and GSK3B, the top CFG scoring validated biomarkers, as well as PIK3C3, have anti-apoptotic and neurotrophic effects, are decreased in expression in suicidality and are known targets of the anti-suicidal mood stabilizer drug lithium, which increases their expression and/or activity. Circadian clock genes were overrepresented among the top markers. Notably, PER1, increased in expression in suicidality, had an AUC of 84% for predicting future hospitalizations, and CSNK1A1, decreased in expression, had an AUC of 96% for predicting future hospitalizations. Circadian clock abnormalities are related to mood disorder, and sleep abnormalities have been implicated in suicide. Docosahexaenoic acid signaling was one of the top biological pathways overrepresented in validated biomarkers, which is of interest given the potential therapeutic and prophylactic benefits of omega-3 fatty acids. Some of the top biomarkers from the current work in women showed co-directionality of change in expression with our previous work in men, whereas others had changes in opposite directions, underlying the issue of biological context and differences in suicidality between the two genders. With this study, we begin to shed much needed light in the area of female suicidality, identify useful objective predictors and help understand gender commonalities and differences. During the conduct of the study, one participant committed suicide. In retrospect, when the analyses were completed, her UP-Suicide risk prediction score was at the 100 percentile of all participants tested.

Gene Expression in Biopsies of Acute Rejection and Interstitial Fibrosis/Tubular Atrophy Reveals Highly Shared Mechanisms That Correlate With Worse Long-Term Outcomes.

Interstitial fibrosis and tubular atrophy (IFTA) is found in approximately 25% of 1-year biopsies posttransplant. It is known that IFTA correlates with decreased graft survival when histological evidence of inflammation is present. Identifying the mechanistic etiology of IFTA is important to understanding why long-term graft survival has not changed as expected despite improved immunosuppression and dramatically reduced rates of clinical acute rejection (AR) (Services UDoHaH. http://www.ustransplant.org/annual_reports/current/509a_ki.htm). Gene expression profiles of 234 graft biopsy samples were obtained with matching clinical and outcome data. Eighty-one IFTA biopsies were divided into subphenotypes by degree of histological inflammation: IFTA with AR, IFTA with inflammation, and IFTA without inflammation. Samples with AR (n = 54) and normally functioning transplants (TX; n = 99) were used in comparisons. A novel analysis using gene coexpression networks revealed that all IFTA phenotypes were strongly enriched for dysregulated gene pathways and these were shared with the biopsy profiles of AR, including IFTA samples without histological evidence of inflammation. Thus, by molecular profiling we demonstrate that most IFTA samples have ongoing immune-mediated injury or chronic rejection that is more sensitively detected by gene expression profiling. These molecular biopsy profiles correlated with future graft loss in IFTA samples without inflammation.

Understanding and predicting suicidality using a combined genomic and clinical risk assessment approach.

Worldwide, one person dies every 40 seconds by suicide, a potentially preventable tragedy. A limiting step in our ability to intervene is the lack of objective, reliable predictors. We have previously provided proof of principle for the use of blood gene expression biomarkers to predict future hospitalizations due to suicidality, in male bipolar disorder participants. We now generalize the discovery, prioritization, validation, and testing of such markers across major psychiatric disorders (bipolar disorder, major depressive disorder, schizoaffective disorder, and schizophrenia) in male participants, to understand commonalities and differences. We used a powerful within-participant discovery approach to identify genes that change in expression between no suicidal ideation and high suicidal ideation states (n=37 participants out of a cohort of 217 psychiatric participants followed longitudinally). We then used a convergent functional genomics (CFG) approach with existing prior evidence in the field to prioritize the candidate biomarkers identified in the discovery step. Next, we validated the top biomarkers from the prioritization step for relevance to suicidal behavior, in a demographically matched cohort of suicide completers from the coroner's office (n=26). The biomarkers for suicidal ideation only are enriched for genes involved in neuronal connectivity and schizophrenia, the biomarkers also validated for suicidal behavior are enriched for genes involved in neuronal activity and mood. The 76 biomarkers that survived Bonferroni correction after validation for suicidal behavior map to biological pathways involved in immune and inflammatory response, mTOR signaling and growth factor regulation. mTOR signaling is necessary for the effects of the rapid-acting antidepressant agent ketamine, providing a novel biological rationale for its possible use in treating acute suicidality. Similarly, MAOB, a target of antidepressant inhibitors, was one of the increased biomarkers for suicidality. We also identified other potential therapeutic targets or biomarkers for drugs known to mitigate suicidality, such as omega-3 fatty acids, lithium and clozapine. Overall, 14% of the top candidate biomarkers also had evidence for involvement in psychological stress response, and 19% for involvement in programmed cell death/cellular suicide (apoptosis). It may be that in the face of adversity (stress), death mechanisms are turned on at a cellular (apoptosis) and organismal level. Finally, we tested the top increased and decreased biomarkers from the discovery for suicidal ideation (CADM1, CLIP4, DTNA, KIF2C), prioritization with CFG for prior evidence (SAT1, SKA2, SLC4A4), and validation for behavior in suicide completers (IL6, MBP, JUN, KLHDC3) steps in a completely independent test cohort of psychiatric participants for prediction of suicidal ideation (n=108), and in a future follow-up cohort of psychiatric participants (n=157) for prediction of psychiatric hospitalizations due to suicidality. The best individual biomarker across psychiatric diagnoses for predicting suicidal ideation was SLC4A4, with a receiver operating characteristic (ROC) area under the curve (AUC) of 72%. For bipolar disorder in particular, SLC4A4 predicted suicidal ideation with an AUC of 93%, and future hospitalizations with an AUC of 70%. SLC4A4 is involved in brain extracellular space pH regulation. Brain pH has been implicated in the pathophysiology of acute panic attacks. We also describe two new clinical information apps, one for affective state (simplified affective state scale, SASS) and one for suicide risk factors (Convergent Functional Information for Suicide, CFI-S), and how well they predict suicidal ideation across psychiatric diagnoses (AUC of 85% for SASS, AUC of 89% for CFI-S). We hypothesized a priori, based on our previous work, that the integration of the top biomarkers and the clinical information into a universal predictive measure (UP-Suicide) would show broad-spectrum predictive ability across psychiatric diagnoses. Indeed, the UP-Suicide was able to predict suicidal ideation across psychiatric diagnoses with an AUC of 92%. For bipolar disorder, it predicted suicidal ideation with an AUC of 98%, and future hospitalizations with an AUC of 94%. Of note, both types of tests we developed (blood biomarkers and clinical information apps) do not require asking the individual assessed if they have thoughts of suicide, as individuals who are truly suicidal often do not share that information with clinicians. We propose that the widespread use of such risk prediction tests as part of routine or targeted healthcare assessments will lead to early disease interception followed by preventive lifestyle modifications and proactive treatment.

Molecular classifiers for acute kidney transplant rejection in peripheral blood by whole genome gene expression profiling.

There are no minimally invasive diagnostic metrics for acute kidney transplant rejection (AR), especially in the setting of the common confounding diagnosis, acute dysfunction with no rejection (ADNR). Thus, though kidney transplant biopsies remain the gold standard, they are invasive, have substantial risks, sampling error issues and significant costs and are not suitable for serial monitoring. Global gene expression profiles of 148 peripheral blood samples from transplant patients with excellent function and normal histology (TX; n = 46), AR (n = 63) and ADNR (n = 39), from two independent cohorts were analyzed with DNA microarrays. We applied a new normalization tool, frozen robust multi-array analysis, particularly suitable for clinical diagnostics, multiple prediction tools to discover, refine and validate robust molecular classifiers and we tested a novel one-by-one analysis strategy to model the real clinical application of this test. Multiple three-way classifier tools identified 200 highest value probesets with sensitivity, specificity, positive predictive value, negative predictive value and area under the curve for the validation cohort ranging from 82% to 100%, 76% to 95%, 76% to 95%, 79% to 100%, 84% to 100% and 0.817 to 0.968, respectively. We conclude that peripheral blood gene expression profiling can be used as a minimally invasive tool to accurately reveal TX, AR and ADNR in the setting of acute kidney transplant dysfunction.

Polymorphisms and mutations of human TMPRSS6 in iron deficiency anemia.

Male subjects with iron deficiency from the general population were examined for polymorphisms or sporadic mutations in TMPRSS6 to identify genetic risk factors for iron deficiency anemia. Three uncommon non-synonymous polymorphisms were identified, G228D, R446W, and V795I (allele frequencies 0.0074, 0.023 and 0.0074 respectively), of which the R446W polymorphism appeared to be overrepresented in the anemic population. In addition, three children with iron refractory iron deficiency anemia, and one sibling with iron responsive iron deficiency anemia were also examined for polymorphisms or sporadic mutations in TMPRSS6. Two children (family 1) were compound heterozygotes for a L674F mutation and a previously described splicing defect predicted to cause skipping of exon 13 (IVS13+1 G>A). One child from the second family was homozygous for a deletion (497T) causing a frameshift (L166X+36) and premature termination. The sibling and mother from the second family were compound heterozygotes for the L166X mutation and the uncommon R446W polymorphism. Although in vitro expression studies demonstrated that the R446W isoform was biologically similar to wildtype Tmprss6, clinical data indicate that the R446W produces a milder disease when carried in trans with severe mutation in Tmprss6. The four children carrying mutations in TMPRSS6 all exhibited inappropriately high urinary hepcidin levels for the degree of iron deficiency.

Erythrocyte glutathione synthetase deficiency leads not only to glutathione but also to glutathione-S-transferase deficiency.

Glutathione synthetase (GSH-S) is one of the two known hereditary causes of glutathione deficiency. We describe a family whose two children have hemolytic anemia. The children's erythrocytes lack GSH and are severely deficient in GSH-S activity. No neurologic findings or 5-oxoprolinuria were present. A concurrent deficiency of glutathione-S-transferase (GST) was also detected in the erythrocytes. Residual glutathione could be detected in the erythrocytes using a sensitive cycling assay. The deficiency was found to be most severe in reticulocyte-depleted preparations. The GSH-S activity of the erythrocytes of the parents was one-half normal, while the glutathione S-transferase activity was normal. We conclude that the primary defect is one of GSH-S. Glutathione stabilizes GST in vitro, and it is assumed that the deficiency of GST in the erythrocytes of the patients is due to the instability of this enzyme in the absence of adequate intracellular GSH levels.

Chronic non-spherocytic hemolytic anemia associated with severe neurological disease due to gamma-glutamylcysteine synthetase deficiency in a patient of Moroccan origin.

A previously undescribed mutation of hereditary gamma-glutamylcysteine synthetase (GCS) deficiency was found in a 5 year old boy of Moroccan origin. He presented with chronic haemolytic anaemia, delayed psychomotor development and progressive motor sensitive neuropathy of lower extremities. The parents were third degree relatives. The activity of glycolytic enzymes were found to be normal in the propositus, his parents and a sister, but and a complete lack of GSH was found in the propositus. Accordingly, the measurement of de novo GSH synthetic enzymes was undertaken, and severe GCS deficiency was found in the propositus. Both parents and his sister presented GCS activity ranging from 69% to 90% of normal. GCS gene sequencing showed that the propositus was homozygous for a 1241C>T mutation in exon 11 and both parents and his sister were heterozygous. This mutation predicts a Pro414Leu amino acid substitution. Even though the homology between GCS and crystallographically solved, functionally related proteins is not very high, a three-dimensional model of GCS was derived using Modeller Software. GCS deficiency is a very rare autosomal recessive disorder reported so far in only 8 unrelated probands with severe haemolytic anaemia. In only 3 of these was the anaemia associated with severe neurological dysfunction. We report here the fourth case of GCS deficiency presenting neuropathy, giving further support to the eventual relationship between this enzymopathy and neurological damage.

Gaucher disease. Clinical, laboratory, radiologic, and genetic features of 53 patients.

We have reviewed our experiences with the clinical, laboratory, radiologic, and genetic features of 53 patients with Gaucher disease. Most were evaluated during early adult life, with a mean age of 33 years. Our patients were evaluated in a referral center, and therefore the data need to be interpreted with caution when applied to the general patient population, which includes a greater proportion of very mild cases. Thirty-nine patients were Ashkenazi Jews, 13 were non-Jewish and 1 was half-Jewish. The most common presenting symptom was bleeding related to splenomegaly and thrombocytopenia. The chronic symptoms, evaluated an average of 20 years after the diagnosis had been established, were mainly skeletal. Splenectomy had been performed in 43% of our patients and there was no evidence that this procedure accelerated the progression of liver and bone involvement. DNA from the patients was examined for 20 different mutations. The association between the 1226G/1226G genotype and a milder clinical course, and between the 1226G/84GG and 1226/1448C genotypes with more severe clinical manifestations, was confirmed. Repeated follow-up examinations in 29 patients revealed that in the majority of the patients, progression of the disease occurs during childhood, adolescence, or early adulthood with a marked tendency for stabilization thereafter. This observation suggests that Gaucher disease in most of the patients is not a relentless progressive disorder but a rather stable disorder during adulthood. The indications for the newly introduced intravenous enzyme replacement therapy as well as of future experimental treatments should be examined in the light of the natural history of the disease.

Mechanism of improved maintenance of 2,3-diphosphoglycerate in stored blood by the xanthone compound 2-(2-hydroxyethoxy)-6-(1-H-tetrazole-5-yl)xanthen-9-one (BW A440C).

The effect of the xanthone derivative 2-(2-hydroxyethoxy)-6-(1-H-tetrazole-5-yl)xanthen-9-one (BW A440C) on red cells was studied. When added to stored red cells at a concentration of 6 mM, greatly improved preservation of 2,3-diphosphoglycerate (2,3-DPG) was observed. There was no effect on internal pH of the erythrocyte. At a concentration 0.500 mM, many red cell enzyme activities were inhibited completely. At a 0.500 mM concentration, however, inhibition of pyruvate kinase and diphosphoglycerate phosphatase was most striking. Inhibition of either of these enzymes could result in elevation of 2,3-DPG levels. BW A440C in concentrations which elevated 2,3-DPG levels in humans caused a decrease in 2,3-DPG levels in rabbits and markedly impaired the viability of 21-day stored rabbit erythrocytes.

Falsely normal value in fluorometric transferase screening of galactosemic blood. A cautionary note.

A blood sample from a galactosemic infant gave a normal result with the fluorescent screening test for galactose-1-phosphate uridyl transferase. The generation of fluorescence from this sample was found to be property of the plasma; the erythrocytes manifested no galactose-1-phosphate uridyl transferase activity. The plasma was found to contain a high level of isocitrate dehydrogenase, presumably a result of the infant's liver disease, and of isocitrate, presumably derived from citrate in the anticoagulant solution by action of aconitase derived from leukocytes which lysed during shipment. The oxidation of the isocitrate by the dehydrogenase apparently resulted in reduction of NADP to NADPH. False negative results have not been reported previously using the fluorescent transferase assay. They can be avoided in the future by using EDTA rather than citrate as an anticoagulant, particularly if blood samples are to be shipped at ambient temperature.

Improved assay of the enzymes of glutathione synthesis: gamma-glutamylcysteine synthetase and glutathione synthetase.

New methods for the estimation of red cell gamma-glutamylcysteine synthetase and glutathione synthetase have been developed. gamma-32P ATP is allowed to equilibrate until the gamma and beta phosphate groups are equally labelled. The amount of 32Pi released in the presence of glutamic acid and cysteine, the substrates for GC-S or in the presence of gamma-glutamylcysteine and glycine, the substrates of GSH-S, is measured. This is accomplished by extraction of the phosphomolybdate complex into isobutanol-benzene. The methods are linear with time and hemolysate concentration. Normal values are presented.

The facile detection of the nt 1226 mutation of glucocerebrosidase by 'mismatched' PCR.

The most common Gaucher disease-producing mutation among Ashkenazi Jews is an A----G substitution at cDNA nt 1226 (genomic nt 5841). We describe a simple method for detecting this mutation both in genomic DNA and in cDNA by performing polymerase chain reaction (PCR) using a 5'-primer mismatched at one nucleotide so as to create an Xho I restriction site. When the mutation is present. the 105 bp fragment formed is cleaved to 89 and 16 nt fragments. The 89 bp fragment is easily visualized on a gel making it possible to distinguish individuals who do not have the mutation from heterozygotes and homozygotes.

Analysis of HFE-codon 63/282 (H63D/C282Y) gene variants in mexican mestizos. Blood donors and patients with hereditary hemochromatosis.

BACKGROUND: The prevalence of hereditary hemochromatosis (HH) (H63D/C282Y) gene variants in Mexico is unknown. METHODS: Using amplification refractory mutation system polymerase chain reaction, an analysis of HFE-codon 63/282 (H63D/C282Y) gene variants was performed in a group of 153 Mexican mestizo blood donors and six individuals with familial iron overload. RESULTS: In normal blood donors, three heterozygotes for the C282Y mutation (2.0%) were found, whereas 18 heterozygotes and one homozygote for the H63D mutation (11.8% and 0.6%, respectively) were identified; there was one compound heterozygote for the C282Y/H63D mutation. These data resulted in allele frequencies of 0.013 (+/-0. 2%, alpha = 0.05) and 0.062 (+/-0.9%, alpha = 0.05), respectively, for these two mutations, results similar to those found in whites. In the six patients with the HH phenotype, two were found to be heterozygous for C282Y and one heterozygous for H63D; three individuals with HH had no gene mutations. Two heterozygous HH individuals were found to have iron overload associated with other conditions: one heterozygous for C282Y infected with HIV, and another heterozygous for H63D with heterozygous beta-thalassemia. CONCLUSIONS: The prevalence of C282Y and H63D HFE gene mutations in Mexican mestizos is similar to that found in other populations. In addition, other gene mutations responsible for HH in the Mexican mestizo population should be investigated, because, in three of six individuals with the HH phenotype, neither of the two mutations was recorded.

Large-scale screening for HFE mutations: methodology and cost.

Large-scale detection of mutations at the DNA level requires the development of cost-effective methods for the screening of thousands of samples. Hemochromatosis is an appropriate testing ground for the development of such technologies, and we report the methods that we have developed to screen large numbers of samples using equipment available in most laboratories. We are able to examine DNA samples for two mutations in the HFE gene at a cost of only slightly over $8 per sample, a cost that includes overhead and the approximately 40 hr per week of technician time required to perform the studies. The technologies involved in mutation analysis are evolving rapidly and ultimately more highly automated, lower-cost technologies may become available. At present, however, we find the methodology described to be very suitable for large-scale, low-cost mutation screening.