Characterization of humoral and cell-mediated immunity induced by mRNA vaccines expressing influenza hemagglutinin stem and nucleoprotein in mice and nonhuman primates.

In response to immune pressure, influenza viruses evolve, producing drifted variants capable of escaping immune recognition. One strategy for inducing a broad-spectrum immune response capable of recognizing multiple antigenically diverse strains is to target conserved proteins or protein domains. To that end, we assessed the efficacy and immunogenicity of mRNA vaccines encoding either the conserved stem domain of a group 1 hemagglutinin (HA), a group 2 nucleoprotein (NP), or a combination of the two antigens in mice, as well as evaluated immunogenicity in naïve and influenza seropositive nonhuman primates (NHPs). HA stem-immunized animals developed a robust anti-stem antibody binding titer, and serum antibodies recognized antigenically distinct group 1 HA proteins. These antibodies showed little to no neutralizing activity in vitro but were active in an assay measuring induction of antibody-dependent cellular cytotoxicity. HA-directed cell-mediated immunity was weak following HA stem mRNA vaccination; however, robust CD4 and CD8 T cell responses were detected in both mice and NHPs after immunization with mRNA vaccines encoding NP. Both HA stem and NP mRNA vaccines partially protected mice from morbidity following lethal influenza virus challenge, and superior efficacy against two different H1N1 strains was observed when the antigens were combined. In vivo T cell depletion suggested that anti-NP cell-mediated immunity contributed to protection in the mouse model. Taken together, these data show that mRNA vaccines encoding conserved influenza antigens, like HA stem and NP in combination, induce broadly reactive humoral responses as well as cell-mediated immunity in mice and NHPs, providing protection against homologous and heterologous influenza infection in mice.

Photoprotection for all: Current gaps and opportunities.

The effects of solar radiation on human skin differ based on the skin phototype, presence or absence of photodermatoses, biologic capacity to repair DNA damage, wavelength, intensity of sun exposure, geographic latitude, and other factors, underscoring the need for a more tailored approach to photoprotection. To date, the focus of photoprotection guidelines has been to prevent sunburn and DNA damage induced by UV radiation, both UVB and UVA; however, several recent studies have shown that visible light also generates reactive oxygen and nitrogen species that can contribute to skin damage and pigmentation on the skin, particularly in people with skin of color. Therefore, individuals with dark skin, while naturally better protected against UVB radiation by virtue of the high eumelanin content in melanocytes, may need additional protection from visible light-induced skin damage. The current options for photoprotection products need to expand, and potential strategies against visible light include the addition of iron oxide, titanium dioxide, and biologically relevant antioxidants to sunscreen formulations as well as supplementation with orally active antioxidants.

Vaccine Hyporesponse Induced by Individual Antibiotic Treatment in Mice and Non-Human Primates Is Diminished upon Recovery of the Gut Microbiome.

Emerging evidence demonstrates a connection between microbiome composition and suboptimal response to vaccines (vaccine hyporesponse). Harnessing the interaction between microbes and the immune system could provide novel therapeutic strategies for improving vaccine response. Currently we do not fully understand the mechanisms and dynamics by which the microbiome influences vaccine response. Using both mouse and non-human primate models, we report that short-term oral treatment with a single antibiotic (vancomycin) results in the disruption of the gut microbiome and this correlates with a decrease in systemic levels of antigen-specific IgG upon subsequent parenteral vaccination. We further show that recovery of microbial diversity before vaccination prevents antibiotic-induced vaccine hyporesponse, and that the antigen specific IgG response correlates with the recovery of microbiome diversity. RNA sequencing analysis of small intestine, spleen, whole blood, and secondary lymphoid organs from antibiotic treated mice revealed a dramatic impact on the immune system, and a muted inflammatory signature is correlated with loss of bacteria from Lachnospiraceae, Ruminococcaceae, and Clostridiaceae. These results suggest that microbially modulated immune pathways may be leveraged to promote vaccine response and will inform future vaccine design and development strategies.

Efficacy of Nonprescription Moisturizers for Atopic Dermatitis: An Updated Review of Clinical Evidence.

Twice-daily moisturization is recommended by international guidelines as the bedrock of the management of atopic dermatitis (AD). Moisturizers should be selected based on proven clinical effectiveness in improving the skin barrier and improving the symptoms of AD. We searched the PubMed database for clinical trials assessing daily moisturization for the treatment of AD published between 2006 and 2019. Studies had to assess the efficacy of commercially available moisturizers using objective measures of corneometry, transepidermal water loss, or incidence of flare as endpoints, and treatments had to be currently available to patients. Clinical studies showed that moisturization (typically twice daily) significantly improved the skin barrier in adults and children with AD. Longer-term flare studies showed that daily moisturization reduced the incidence of flares and extended the time between flares. Proactive moisturization of infants at high risk of developing AD may reduce its manifestation. Therapeutic moisturizers for AD are specifically formulated with ingredients that target symptoms of AD, such as itch, inflammation, or compromised skin barrier. The US FDA requires that any moisturizer available in the USA and claiming to treat AD must contain colloidal oatmeal. Healthcare providers can maximize compliance and outcomes by educating patients on the benefits of liberally applying a therapeutic moisturizer twice daily to support the skin barrier and help reduce the incidence of flares. Specific recommendations should be for clinically tested moisturizers evaluated using objective, validated skin assessments.

Effective Tyrosinase Inhibition by Thiamidol Results in Significant Improvement of Mild to Moderate Melasma.

Melasma is a pigmentary disorder characterized by hyperpigmented patchy skin in sun-exposed areas, especially the face. Treatment of melasma can be challenging because long-term therapy is required, reoccurrence is common, and existing therapies are insufficient and unsatisfactory. To investigate new treatment options, we performed an exploratory double-blinded, randomized split-face study to assess the efficacy of the tyrosinase inhibitor Thiamidol compared to hydroquinone in women with mild to moderate melasma. After 12 weeks, modified Melasma Area and Severity Index scores significantly improved on both the Thiamidol-treated and the hydroquinone-treated sides of the face. Additionally, Thiamidol treatment improved modified Melasma Area and Severity Index scores significantly better than hydroquinone, and more subjects improved following treatment with Thiamidol (79%) compared with hydroquinone (61%). During treatment, no subjects displayed worsening of modified Melasma Area and Severity Index scores on the Thiamidol-treated side, while approximately 10% of the subjects showed a worsening of modified Melasma Area and Severity Index scores on the hydroquinone-treated side. All subjects routinely used sunscreens and consistent results were obtained in low and in high UV ambient conditions. Subjects rated the efficacy of the Thiamidol formulation significantly better with regard to overall decreased intensity of dark spots and their overall appearance throughout the study. Thiamidol was well-tolerated and well-perceived and represents an effective agent to reduce hyperpigmentation.

pH and Microbial Infections.

Maintenance of an acidic stratum corneum pH is a major component of the skin's protective system and creates a hostile environment for colonization with pathogenic microorganisms. This barrier can however be overcome on healthy and in particular on compromised skin. Mycosis, diaper/incontinence dermatitis and wound healing are examples of cases where microbial infection is promoted by the altered skin conditions or environment. Fungi have a complex system that senses ambient pH that leads to metabolic responses allowing adhesion, growth and invasion, as microbial metabolites further increase skin pH resulting in a clinically manifest infection (mycosis). Diabetic patients with a higher pH in intertriginous areas are particularly vulnerable to candidiasis. In diaper and incontinence dermatitis, the increase in skin pH and damage to the skin barrier function is triggered by the contact with urine and faeces with or without occlusion and maintained by host and microbial enzymes and metabolites. This leads to the reduction of the protective resident microflora and fungal overgrowth, mostly with Candida albicans. Skin care with slightly acidic products may help to prevent and treat this kind of dermatitis. Wound healing is a complex sequence of biologic events correlated with ambient pH, which influences the different phases of the healing process. The pH determines the appropriate activity of immune cells and key enzymes as well as biofilm formation. Chronic wounds emerging from the disruption of the healing process are characterized by a neutral to slightly alkaline pH and may benefit from wound pH monitoring and therapeutic acidification.

Stand-alone Emollient Treatment Reduces Flares After Discontinuation of Topical Steroid Treatment in Atopic Dermatitis: A Double-blind, Randomized, Vehicle-controlled, Left-right Comparison Study.

Prevention of the flares is a main goal in the long-term treatment of atopic dermatitis (AD). Therefore we investigated the efficacy of a water-in-oil emollient, containing licochalcone A, omega-6-fatty acids, ceramide 3 and glycerol, for prevention of the flares in adults with mild to moderately severe AD, treated with topical steroids, that led to clearing of the inflammatory lesions and had been discontinued prior to inclusion. The study was a 12-week, double-blind, randomized, vehicle-controlled, left-right comparison test with the number of relapses, defined as re-occurrence of erythema for at least 3 consecutive days, considered the primary outcome. Compared with the vehicle, the active formulation significantly reduced the number of relapses and maintained the barrier homeostasis of the respective arm. To the best of knowledge, this is the first study to show prevention of the AD flares by the use of stand-alone emollient treatment, based on comparison with the corresponding vehicle while excluding concomitant/rescue medications.

Childhood maltreatment and context dependent empathic accuracy in adult romantic relationships.

OBJECTIVES: Childhood maltreatment, that is neglect and abuse, are associated with difficulties in adult relationship functioning. We tested whether childhood maltreatment changes the presence of a relationship protective mechanism, called motivated inaccuracy. It describes a decrease in romantic couples' empathic accuracy, (EA), that is, their correct understanding of the partners' thoughts and feelings, in situations that pose a potential threat to the stability of the relationship. With this, couples seem to protect their relationship stability from their partners' potentially destabilizing mental contents. METHOD: Romantic couples were videotaped while discussing (a) their favorite film-genre (neutral/positive), (b) their most relevant fear of the past year (personally threatening), and (c) a reason that might lead to a break-up in their relationship (relationship-threatening). EA was measured by the overlap between participants' judgments of their partners' feelings and the partners' self-rated actual feeling, using a continuous video rating of the interactions. Childhood neglect and abuse were retrospectively assessed by a questionnaire. RESULTS: Overall, participants decreased their EA for each other in the relationship-threatening versus personally threatening conversation, replicating motivated inaccuracy. However, when individuals with high levels of reported childhood neglect felt threatened by the relationship-threatening condition, they did not show this relationship protective mechanism, that is, they showed maintained EA scores. Abuse in childhood did not influence the presence of motivated inaccuracy. CONCLUSIONS: Childhood neglect might influence adult romantic relationship functioning by leading to a lack of motivated inaccuracy during relationship-threatening situations. An altered threat coping strategy might cause the inability to protect oneself from relationship-threatening information. (PsycINFO Database Record

Steroid-Free Over-the-Counter Eczema Skin Care Formulations Reduce Risk of Flare, Prolong Time to Flare, and Reduce Eczema Symptoms in Pediatric Subjects With Atopic Dermatitis.

INTRODUCTION: Atopic dermatitis (AD) is a chronic skin condition associated with decreased barrier function resulting in periodic flare-ups of erythematous and pruritic lesions. Guidelines recommend daily treatment of atopic skin with emollient moisturizers for prevention of flares and maintenance of the flare-free state. This study evaluated the efficacy of 2 steroid-free, nonprescription eczema skin care formulations for reducing the risk of flare and relieving symptoms in infants and children with AD: Body Cream for the daily maintenance treatment of atopic skin and Flare Treatment for the treatment of atopic flares. METHODS: After a 2-week washout period, subjects (N=45; mean age 3.5 years) were randomized to cleanser plus daily moisturizing with Body Cream (moisturizer group) or cleanser only (control group) for 6 months or until flare. Subjects experiencing flare received Flare Treatment for 4 weeks. RESULTS: The incidence of flare was significantly lower in the moisturizer group compared with the control group (21% vs 65%; P=.006), while the median time to flare was shorter in the control group (28 vs >180 days). Risk of flare was reduced by 44.1% after 6 months of Body Cream application. Flare Treatment reduced overall eczema symptom severity at week 2 and week 4; 78.9% of flares had improved or cleared at week 4. CONCLUSIONS: Body Cream reduced the incidence of flare and the time to flare, reinforcing guidelines that daily emollient therapy should be an integral part of the maintenance treatment plan for the prevention of disease flares. Body Cream and Flare Treatment are effective over-the-counter steroid-free options for management of AD in children.

Efficacy and Tolerability of Steroid-Free, Over-the-Counter Treatment Formulations in Infants and Children With Atopic Dermatitis.

BACKGROUND: Two steroid-free, over-the-counter skin protectant products have been developed for the care and treatment of atopic dermatitis (AD)-Eucerin Eczema Relief Body Crème (Body Cream) for daily skin moisturization and Eucerin Eczema Relief Instant Therapy cream (Instant Therapy) for treatment of AD flare-ups. We tested the efficacy and tolerability of these formulations in infants and children with AD. METHODS: Study 1: Body Cream was applied twice daily to the lower legs of 64 children with a history of AD (aged 3 months to 12 years) for 14 days. Study 2: Instant Therapy was applied to active lesions and surrounding skin of 29 children (aged 3 months to 12 years) with active atopic lesions. Assessments were performed at baseline and Days 7 and 14. Symptoms were assessed using the Atopic Dermatitis Severity Index in Study 2. RESULTS: Body Cream significantly improved skin hydration and reduced itching, burning/stinging, erythema, and tactile roughness. Instant Therapy significantly improved skin hydration and AD symptoms, notably pruritus, erythema, and lichenification. Both products were safe and well tolerated. DISCUSSION: Body Cream and Instant Therapy were effective and well tolerated in the treatment of AD in children. These products provide steroid-free, nonprescription therapy for the maintenance and treatment of acute eczema and were proven effective and safe in infants as young as 3 months.

Steroid-free emollient formulations reduce symptoms of eczema and improve quality of life.

Two over-the-counter products have been clinically tested for efficacy and tolerability in the treatment of atopic dermatitis. Study 1 evaluated a daily maintenance Body Cream (Eucerin Eczema Relief Body Crème) applied twice daily for 14 days, followed by treatment withdrawal for 5 days (regression period) in subjects with a history of atopic dermatitis. Study 2 evaluated an acute treatment (Eucerin Eczema Relief Instant Therapy [Instant Therapy]) for active atopic dermatitis lesions administered for 14 days. Skin barrier function, hydration, tolerability, and relief of symptoms were assessed at baseline, day 7, and day 14. Study 2 also measured itch relief and treatment impact on work, social activities, and sleep. Body Cream significantly improved skin hydration and barrier function (P<.001) at 14 days, with improvements persisting through the 5-day regression phase. Itching was significantly improved in 93.8% of subjects (P<.001). Instant Therapy treatment of atopic dermatitis lesions significantly improved skin hydration and barrier function, as well as symptoms of erythema, pruritus, excoriation, and lichenification, with rapid improvement of itch reported within minutes of the first treatment application. Instant Therapy significantly reduced itch intensity and frequency, and demonstrated beneficial improvements in subjects' quality of life. Body Cream and Instant Therapy were both safe and well tolerated.

Treatment of xerosis with a topical formulation containing glyceryl glucoside, natural moisturizing factors, and ceramide.

OBJECTIVE: To assess the effects of Light Formulation, an oil-in-water emulsion, and Rich Formulation, a water-in-oil emulsion, for the treatment of xerosis. DESIGN: Two double-blind, vehicle-controlled trials (both formulations); a double-blind, randomized regression study (Rich Formulation); and a single-blind tolerability study (Light Formulation). The two formulations were applied twice daily for two weeks, for five days in the regression study, and twice daily for two weeks in the tolerability study. SETTING: Studies were conducted during winter in Hamburg, Germany. PARTICIPANTS: A total of 169 subjects were enrolled and 154 completed the studies. The majority were between 50 and 80 years of age, women, all with very dry skin. One withdrew because of an incompatibility reaction that reoccurred with the subject's own body lotion after sun exposure. MEASUREMENTS: Skin hydration and skin barrier function with both formulations over two weeks, long-term moisturization effect after discontinuation of Rich Formulation, and symptom improvement and skin tolerability with Light Formulation. RESULTS: Vehicle-controlled studies of Light and Rich Formulations demonstrated significantly improved hydration at Weeks 1 and 2 versus the untreated site and vehicles, and significantly reduced transepidermal water loss versus untreated site and basic vehicle. Both products significantly decreased visible dryness and tactile roughness. In the regression study, Rich Formulation maintained significant moisturization six days after treatment discontinuation. Light Formulation reduced symptoms of itching, burning, tightness, tingling, and feeling of dryness. CONCLUSION: These formulations represent a new approach for the treatment of xerosis by addressing multiple key deficiencies in skin hydration.

An over-the-counter moisturizer is as clinically effective as, and more cost-effective than, prescription barrier creams in the treatment of children with mild-to-moderate atopic dermatitis: a randomized, controlled trial.

BACKGROUND: Atopic dermatitis (AD) is a prevalent skin disorder with significant cost of treatment. Several prescription device moisturizers have been approved by the FDA to treat AD but are significantly more expensive than well-crafted over-the-counter (OTC) moisturizers. No studies have been performed to compare both the clinical efficacy and cost-efficacy of these prescription devices to OTC moisturizers. PURPOSE: The purpose of this study is to compare the clinical efficacy and cost-efficacy of a glycyrrhetinic acid-containing barrier repair cream (BRC-Gly, Atopiclair®), a ceramide-dominant barrier repair cream (BRC-Cer, EpiCeram®) and an OTC petroleum-based skin protectant moisturizer (OTC-Pet, Aquaphor Healing Ointment®) as monotherapy for mild-to-moderate AD in children. METHODS: Thirty-nine patients, age 2-17 years, with mild-to-moderate AD were randomized 1:1:1 to receive one of three treatments-BRC-Gly, BRC-Cer or OTC-Pet-with instructions to apply the treatment three times daily for three weeks. Disease severity and improvement was assessed at baseline and on days 7 and 21. RESULTS: No statistically significant difference for any efficacy assessment was found between the three groups at each time point. The OTC-Pet was found to be at least 47 times more cost-effective than BRC-Gly or BRC-Cer. LIMITATIONS: The relatively small sample size of 39 subjects was not sufficient to establish OTC-Pet as superior treatment in AD. CONCLUSIONS: OTC-Pet is as effective in treating mild-to-moderate AD as both BRC-Gly and BRC-Cer and is at least 47 times more cost-effective. NAME OF REGISTRY: II-AF-ATD-Aquaphor, Comparing the Efficacy and Cost-Effectiveness of Aquaphor to Atopiclair and EpiCeram in Children with Mild to Moderate Atopic Dermatitis. REGISTRATION IDENTIFIER: NCT01093469.

Irritation and allergy patch test analysis of topical treatments commonly used in wound care: evaluation on normal and compromised skin.

BACKGROUND: Topical agents indicated for the treatment of superficial wounds have the potential to cause irritation or allergic contact dermatitis, particularly when applied to an impaired skin barrier. OBJECTIVE: We sought to compare the irritancy potential of 5 topical wound care products commonly used in dermatologic practice on normal and compromised skin. METHODS: Agents tested included Aquaphor Healing Ointment (AHO) (Beiersdorf Inc, Wilton, CT); bacitracin; Biafine Topical Emulsion (BTE) (OrthoNeutrogena, Los Angeles, CA); Neosporin (Poly/Bac/Neo) (Johnson & Johnson, New Brunswick, NJ); and Polysporin (Poly/Bac) (Johnson & Johnson). Study 1 assessed cumulative irritation using a modified human repeat insult patch test on normal back skin with an induction phase (test materials applied under occlusive patch 9 times at 48- to 72-hour intervals) and a challenge phase (test materials applied to original and naïve sites for 48 hours, 12-24 days postinduction). Irritation was graded for erythema and type IV allergy skin responses. Study 2 assessed the acute irritation potential of agents on tape-stripped ("wounded") back skin. Test sites were graded for erythema, transepidermal water loss, and skin color (Chroma Meter a∗) (Minolta, Osaka, Japan) at 48 and 72 hours poststripping. RESULTS: In study 1, cumulative irritation testing in 108 subjects classified AHO, bacitracin, Poly/Bac/Neo, and Poly/Bac as "mild," and BTE as "probably mild." In study 2 at 72 hours, mean clinical grading scores were significantly higher for BTE and Poly/Bac/Neo than AHO. Transepidermal water loss and colorimeter a∗ values were significantly lower for AHO and bacitracin compared with BTE. No allergic contact dermatitis was seen in either study. CONCLUSIONS: Patch test studies demonstrated that BTE showed the greatest irritancy potential in both normal and compromised skin whereas AHO showed the least.

Treatment of minor wounds from dermatologic procedures: a comparison of three topical wound care ointments using a laser wound model.

BACKGROUND: Topical antibiotic ointments are commonly used for postoperative wound care after dermatologic procedures such as curettage, electrodessication, or shave removals. Antibiotics have the potential to cause allergic contact dermatitis and increase drug resistance and may not be necessary for the treatment of clean surgical wounds. OBJECTIVE: This study compared the wound healing properties of the topical wound care ointments Aquaphor Healing Ointment (AHO) (Beiersdorf Inc, Wilton, CT), Neosporin (Poly/Bac/Neo) (Johnson & Johnson, New Brunswick, NJ), and Polysporin (Poly/Bac) (Johnson & Johnson) using a laser wound model. METHODS: In this double-blind study, 4 uniform circular erbium/carbon dioxide laser wounds penetrating to the dermis were made in 20 subjects. Each wound was treated 3 times daily for 18 days with AHO, Poly/Bac/Neo, or Poly/Bac, with one wound left untreated (control). Efficacy and safety were assessed using clinical grading, transepidermal water loss, investigator grading of wound appearance, subjective ranking of wound appearance, and adverse event reporting. RESULTS: Significant improvements in erythema (days 7-18), edema (days 4 and 7), epithelial confluence (days 7-18), and general wound appearance (days 7-18) were observed with AHO compared with Poly/Bac/Neo and Poly/Bac (P ≤ .007). No differences were observed between Poly/Bac/Neo and Poly/Bac for any clinical parameters. The average transepidermal water loss value on day 4 was significantly less with AHO compared with the other treatments (P = .0006). Subjects ranked the treated sites as follows: AHO (best), Poly/Bac, and Poly/Bac/Neo. No adverse events were reported. LIMITATIONS: This was a small pilot study using a laser wound model to replicate minor wounds. CONCLUSIONS: AHO demonstrated fast and effective improvements in several wound healing parameters compared with antibiotic-containing treatments.

Skin-lightening effects of a new face care product in patients with melasma.

BACKGROUND: Melasma is a common pigmentation disorder having considerable effect on patients' emotional and psychological well-being. OBJECTIVE: Assessment of efficacy and tolerability of a new face care product for the targeted spot treatment of darker pigmented areas in subjects with melasma and evaluation of effects on patients' quality of life. METHODS: Twenty subjects with melasma were enrolled in this study. Data of 19 participants were available for analysis. Melasma severity was evaluated at baseline, after 4 weeks, and after 8 weeks by using the Melasma Area and Severity Index (MASI). Furthermore, chromametry and digital image analysis of videomicroscopic photographs were performed, and quality of life was measured using the Melasma Quality of Life Scale. RESULTS: The application of the product resulted in a significant lightening of melasma in comparison with baseline and to untreated control areas. The MASI score dropped by more than 40% after 8 weeks. Measurement of skin color by chromametry revealed lightening of pigmented areas and a significant decrease in contrast between melasma and normal-pigmented surrounding skin. These results were confirmed by digital image analysis. Tolerability of the product was rated to be excellent, and patients experienced a significant gain in quality of life. CONCLUSION: The data demonstrate that the new face care product is effective and highly skin tolerable and clearly improves quality of life of patients with melasma.

Mapping determinants of human gene expression by regional and genome-wide association.

To study the genetic basis of natural variation in gene expression, we previously carried out genome-wide linkage analysis and mapped the determinants of approximately 1,000 expression phenotypes. In the present study, we carried out association analysis with dense sets of single-nucleotide polymorphism (SNP) markers from the International HapMap Project. For 374 phenotypes, the association study was performed with markers only from regions with strong linkage evidence; these regions all mapped close to the expressed gene. For a subset of 27 phenotypes, analysis of genome-wide association was performed with >770,000 markers. The association analysis with markers under the linkage peaks confirmed the linkage results and narrowed the candidate regulatory regions for many phenotypes with strong linkage evidence. The genome-wide association analysis yielded highly significant results that point to the same locations as the genome scans for about 50% of the phenotypes. For one candidate determinant, we carried out functional analyses and confirmed the variation in cis-acting regulatory activity. Our findings suggest that association studies with dense SNP maps will identify susceptibility loci or other determinants for some complex traits or diseases.

Genetic analysis of genome-wide variation in human gene expression.

Natural variation in gene expression is extensive in humans and other organisms, and variation in the baseline expression level of many genes has a heritable component. To localize the genetic determinants of these quantitative traits (expression phenotypes) in humans, we used microarrays to measure gene expression levels and performed genome-wide linkage analysis for expression levels of 3,554 genes in 14 large families. For approximately 1,000 expression phenotypes, there was significant evidence of linkage to specific chromosomal regions. Both cis- and trans-acting loci regulate variation in the expression levels of genes, although most act in trans. Many gene expression phenotypes are influenced by several genetic determinants. Furthermore, we found hotspots of transcriptional regulation where significant evidence of linkage for several expression phenotypes (up to 31) coincides, and expression levels of many genes that share the same regulatory region are significantly correlated. The combination of microarray techniques for phenotyping and linkage analysis for quantitative traits allows the genetic mapping of determinants that contribute to variation in human gene expression.

Natural variation in human gene expression assessed in lymphoblastoid cells.

The sequencing of the human genome has resulted in greater attention to genetic variation among individuals, and variation at the DNA sequence level is now being extensively studied. At the same time, it has become possible to study variation at the level of gene expression by various methods. At present, it is largely unknown how widespread this variation in transcript levels is over the entire genome and to what extent individual differences in expression level are genetically determined. In the present study, we used lymphoblastoid cells to examine variation in gene expression and identified genes whose transcript levels differed greatly among unrelated individuals. We also found evidence for familial aggregation of expression phenotype by comparing variation among unrelated individuals, among siblings within families and between monozygotic twins. These observations suggest that there is a genetic contribution to polymorphic variation in the level of gene expression.