Thomas L Dawson

Thomas L Dawson
Agency for Science, Technology and Research (A*STAR) | A*Star · Skin Research Institute Singapore

Ph.D.

About

109
Publications
32,374
Reads
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6,477
Citations
Citations since 2017
44 Research Items
2425 Citations
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20172018201920202021202220230100200300400
20172018201920202021202220230100200300400
Introduction
In 2015 Tom joined A*STAR to develop a hair and skin health program. He leads the A*STAR cutaneous microbiome program, which was recently awarded significant funding (termed the “Asian Skin Microbiome Program” or ASMP). The ASMP will define the healthy skin microbiome and its role in skin homeostasis. Tom remains committed to leveraging microbiology to improve skin health and retains his emphasis on Malassezia, including leading the global consortium on Malassezia phylogeny, physiology, and pathogenesis the “Malassezia Research Consortium”). He also leads a translational program fusing hair shaft biogenesis, biochemical synthesis, and physical measurement to create better hair treatments.
Additional affiliations
May 2015 - present
Agency for Science, Technology and Research (A*STAR)
Position
  • Senior Principal Investigator
October 1998 - February 2015
Procter & Gamble
Position
  • Principal Investigator
November 1994 - October 1998
Duke University Medical Center
Position
  • Research Associate

Publications

Publications (109)
Article
Full-text available
Malassezia form the dominant eukaryotic microbial community on the human skin. The Malassezia genus possesses a repertoire of secretory hydrolytic enzymes involved in protein and lipid metabolism which alter the external cutaneous environment. The exact role of most Malassezia secreted enzymes, including those in interaction with the epithelial sur...
Article
Full-text available
S1.3 Malassezia: genetics, genomics, and biology, September 21, 2022, 11:00 AM - 12:30 PM Objectives Malassezia forms the dominant eukaryotic microbial community on the human skin. The Malassezia genus possesses a repertoire of secretory hydrolytic enzymes involved in protein and lipid metabolism which alter the external cutaneous environment. The...
Article
Identified in the late nineteenth century as a single species residing on human skin, Malassezia is now recognized as a diverse genus comprising 18 species inhabiting not only skin but human gut, hospital environments, and even deep-sea sponges. All cultivated Malassezia species are lipid dependent, having lost genes for lipid synthesis and carbohy...
Article
Skin microbiome sampling is currently performed with tools such as swabs and tape strips to collect microbes from the skin surface. However, these conventional approaches may be unable to detect microbes deeper in the epidermis or in epidermal invaginations. We describe a sampling tool with a depth component, a transepidermal microprojection array...
Article
Full-text available
Malassezia furfur is a common commensal member of human/animal microbiota that is also associated with several pathogenic states. Recent studies report involvement of Malassezia species in Crohn’s disease, a type of inflammatory bowel disease, pancreatic cancer progression, and exacerbation of cystic fibrosis.
Chapter
Effective scalp care includes both treatments of conditions such as dandruff and seborrheic dermatitis (D/SD) as well as prevention of these conditions among susceptible individuals. This chapter covers product choice, explanation of benefits and mechanism, and how best to maximize benefits via patient compliance and usage regimens. The occurrence...
Article
Full-text available
Otitis media (OM) and externa (OE) are painful, recurrent ear conditions. As most otitis publications focus on the bacterial content of childhood ears, there remains a dearth of information regarding the adult ear microbiome including both bacteria and fungi. This study compares the outer ear microbiome of healthy adults to adults affected by OE an...
Preprint
Full-text available
Malassezia species are important fungal skin commensals and are part of the normal microbiota of humans and other animals. However, under certain circumstances these fungi can also display a pathogenic behaviour. For example, Malassezia furfur is a common commensal of human skin, and yet is often responsible for skin disorders but also systemic inf...
Article
Full-text available
Malassezia are common components of human skin, and as the dominant human skin eukaryotic microbe, they take part in complex microbe–host interactions. Other phylogenetically related fungi (including within Ustilagomycotina) communicate with their plant host through bioactive oxygenated polyunsaturated fatty acids, generally known as oxylipins, by...
Article
Full-text available
Malassezia furfur is a yeast species belonging to Malasseziomycetes, Ustilaginomycotina, Basidiomycota that is found on healthy warm-blooded animal skin, but also involved in various skin disorders like seborrheic dermatitis/dandruff and pityriasis versicolor. Moreover, Malassezia are associated with bloodstream infections, Crohn's disease, and pan...
Article
Full-text available
Malassezia are emerging fungal pathogens causing opportunistic skin and severe systemic infection. Nosocomial outbreaks are associated with azole resistance and understanding of the underlying mechanisms are limited to knowledge from other fungal species. Herein, we identified distinct antifungal susceptibility patterns in 26 Malassezia furfur isol...
Article
Full-text available
The skin microbial community is a multifunctional ecosystem aiding prevention of infections from transient pathogens, maintenance of host immune homeostasis, and skin health. A better understanding of the complex milieu of microbe-microbe and host-microbe interactions will be required to define the ecosystem’s optimal function and enable rational d...
Article
Full-text available
Malassezia is the most dominant fungal genus on the human skin surface and is associated with various skin diseases including dandruff and seborrheic dermatitis. Among Malassezia species, Malassezia restricta is the most widely observed species on the human skin. In the current study, we identified a novel dsRNA virus, named MrV40, in M. restricta...
Article
Malassezia restricta and Malassezia globosa are lipid dependent commensal yeasts associated with dandruff. Antifungal actives such as zinc pyrithione are commonly used in antidandruff shampoos, although their efficacy is not clearly demonstrated. In this study, we assessed the efficacy of antifungal treatments on scalp Malassezia via a combination...
Article
Most of the permanent hair dye products contain p-phenylenediamine (PPD), a well-known skin sensitizer. PPD may cause cutaneous reactions and leads to allergic contact dermatitis (ACD), a condition with major medical and financial repercussions. Hair dye-induced ACD represents a growing concern both for consumers and the cosmetics industry. In this...
Article
Full-text available
The use of fluorescent proteins allows a multitude of approaches from live imaging and fixed cells to labeling of whole organisms, making it a foundation of diverse experiments. Tagging a protein of interest or specific cell type allows visualization and studies of cell localization, cellular dynamics, physiology, and structural characteristics. In...
Preprint
The use of fluorescent proteins allows a multitude of approaches from live imaging and fixed cells to labelling of whole organisms, making it a foundation of diverse experiments. Tagging a protein of interest or specific cell type allows visualization and studies of cell localization, cellular dynamics, physiology, and structural characteristics. I...
Article
Full-text available
Malassezia is the most abundant eukaryotic microbial genus on human skin. Similar to many human-residing fungi, Malassezia has high metabolic potential and secretes a plethora of hydrolytic enzymes that can potentially modify and structure the external skin environment. Here we show that the dominant secreted Malassezia protease isolated from cultu...
Article
Full-text available
Genomic rearrangements associated with speciation often result in chromosome number variation among closely related species. Malassezia species show variable karyotypes ranging between 6 and 9 chromosomes. Here, we experimentally identified all 8 centromeres in M. sympodialis as 3 to 5 kb long kinetochore-bound regions spanning an AT-rich core and...
Preprint
Full-text available
Most fungal viruses have been identified in plant pathogens, whereas the presence of viral particles in human pathogenic fungi is less well studied. In the present study, we observed extrachromosomal double-stranded RNA (dsRNA) segments in various clinical isolates of Malassezia species. Malassezia is the most dominant fungal genus on the human ski...
Preprint
Full-text available
34 Genomic rearrangements associated with speciation often result in chromosome number 35 variation among closely related species. Malassezia species show variable karyotypes ranging 36 between 6 and 9 chromosomes. Here, we experimentally identified all 8 centromeres in M. 37 sympodialis as 3 to 5 kb long kinetochore-bound regions spanning an AT-ri...
Article
Many dyes for long-lasting hair coloring contain aromatic amines that undergo oxidative polymerizations, resulting in allergic contact dermatitis, with potential to develop serious toxic effects. Among these amines, para-phenylenediamine (PPD) is a small molecule form of aniline commonly used in beauty products despite being a known allergen to hum...
Article
Full-text available
Commensal fungi such as Malassezia, Candida, and Rhodotorula are common on healthy skin but are also associated with opportunistic invasive and superficial infections. Skin microbial community characterization has been extensively performed worldwide, with a focus on the 16S bacterial community. These studies have focused on geographically distinct...
Article
Background: The role of skin microbiota in acne remains to be fully elucidated. Initial culture-based investigations were hampered by growth rate and selective media bias. Even with less biased genomic methods, sampling, lysis and methodology, the task of describing acne pathophysiology remains challenging. Acne occurs in sites dominated by Cutiba...
Article
New research shows that Malassezia interact directly with the human immune system, and are involved not only in skin health and disease but also gut health and Crohn's disease.
Article
Malassezia yeast exist on all humans and have long been associated with healthy and diseased skin. In this issue of Cell Host & Microbe, Sparber et al. (2019) and Limon et al. (2019) present murine models for Malassezia/host interaction and describe a role for Malassezia in inflammatory skin and gut disease.
Article
Human recorded history is littered with attempts to improve the perceived appearance of scalp hair. Throughout history treatments have included both biological and chemical interventions. Hair “quality” or “perceived appearance” is regulated by multiple biological intervention opportunities: adding more hairs by flipping follicles from Telogen to A...
Preprint
Genomic rearrangements associated with speciation often result in chromosome number variation among closely related species. Malassezia species show variable karyotypes ranging between 6 and 9 chromosomes. Here, we experimentally identified all 8 centromeres in M. sympodialis as 3 to 5 kb long kinetochore-bound regions spanning an AT-rich core and...
Article
An account is provided of the world’s ten most feared fungi. Within areas of interest, we have organized the entries in the order of concern. We put four human pathogens first as this is of concern to most people. This is followed by fungi producing mycotoxins that are highly harmful for humans; Aspergillus flavus, the main producer of aflatoxins,...
Article
Research into biological manipulation of hair "quality" has ebbed and waned but today is in a resurgence. Hair appearance is regulated by multiple intervention opportunities-adding more hairs; increasing hair "amount" by modulating shaft diameter or shape; or, in principle, by altering shaft physical properties by changing its synthesis. It is like...
Article
Full-text available
Malassezia are lipid dependent basidiomycetous yeasts that inhabit the skin and mucosal sites of humans and other warm-blooded animals. They are a major component of the skin mycobiome, based on both culture-based and culture-independent methods that used ITS length polymorphisms assessed by PCR1, ITS meta-barcoding, and whole genome shotgun metage...
Chapter
Hair differs across ethnicities and in changes with age. While limited, most literature agree that Asian ethnicities grey later than Caucasians, beginning at least 5 years later and perhaps regionally more. There are minimal differences in ethnicity with where greying begins, but there are differences comparing between gender. In males, greying beg...
Article
Malassezia are lipid dependent basidiomycetous yeasts that inhabit the skin and mucosa of humans and other warm-blooded animals, and are a major component of the skin microbiome. They occur as skin commensals, but are also associated with various skin disorders and bloodstream infections. The genus currently comprises 17 species and has recently be...
Article
Full-text available
The Structure, Biology & Hair Curl, Colour, and Luster Session included two invited presentations and three selected from submitted abstracts. These presentations taken together highlight current progress in linking follicle biology to the tensile/physical properties of hair. They show progress in understanding the development of the hair fiber, an...
Article
Full-text available
Skin provides the first defense against pathogenic microorganisms and is also colonized by a diverse microbiota. Phylogenetic analysis of whole skin microbiome at different skin sites in health and disease has generated important insights on possible microbial involvement in modulating skin health. However, functional roles of the skin microbial co...
Article
The skin is our first line of defense, protecting us from invasion and evaporation. Its variable structure, changing geography, and complex immune repertoire provide a vast interface for our cutaneous microbial community. Skin is inhabited by many thousands of microbes, but this review focuses on the dominant eukaryote, Malassezia, and its host int...
Data
Supplementary table and figures of this article: Proteogenomics produces comprehensive and highly accurate protein-coding gene annotation in a complete genome assembly of Malassezia sympodialis.
Article
Little is known about the energetics of growing hair follicles, particularly in the mitochondrially abundant bulb. Here, mitochondrial and oxidative metabolism was visualized by multiphoton and light sheet microscopy in cultured bovine hair follicles and plucked human hairs. Mitochondrial membrane potential (ΔΨ), cell viability, reactive oxygen spe...
Article
Full-text available
Complete and accurate genome assembly and annotation is a crucial foundation for comparative and functional genomics. Despite this, few complete eukaryotic genomes are available, and genome annotation remains a major challenge. Here, we present a complete genome assembly of the skin commensal yeast Malassezia sympodialis and demonstrate how proteog...
Article
Androgenetic alopecia (AGA) is the most common progressive form of hair loss that occurs in more than half of men above 50 years (1) . AGA onset is dependent on genetic predisposition and presence of androgen (2, 3) . In AGA patients, hair undergoes shortened anagen phase, progressive miniaturization and subsequent vellus transformation of terminal...
Article
Full-text available
Malassezia is a unique lipophilic genus in class Malasseziomycetes in Ustilaginomycotina, (Basidiomycota, fungi) that otherwise consists almost exclusively of plant pathogens. Malassezia are typically isolated from warm-blooded animals, are dominant members of the human skin mycobiome and are associated with common skin disorders. To characterize t...
Chapter
Normal scalp hygiene requires frequent and effective cleaning of the scalp. Cosmetic shampoos do this effectively while providing conditioning benefits for the hair. For many individuals, this frequent cleaning is sufficient to prevent adverse scalp effects. However, many still suffer from the symptoms of dandruff/seborrheic dermatitis. For this gr...
Article
Full-text available
Several human skin diseases and disorders are associated with two groups of fungi, the dermatophytes and Malassezia. Although these skin-related problems are not generally life threatening, they are among the most common diseases and disorders of mankind. These fungi are phylogenetically divergent, with the dermatophytes within the Ascomycota and M...
Patent
Full-text available
The present invention relates to skin care compositions comprising blends of camellia and feverfew serum fractions and/or kelp and parsley serum fractions. The skin care compositions also comprise a dermatologically acceptable carrier. The invention also relates to methods for increasing melanin production in skin by topically applying the skin car...
Patent
Full-text available
A hair care composition and method of using the composition is provided that can increase the appearance of thicker and/or fuller hair and/or delay the appearance of gray hair to provide healthy and younger looking hair.
Article
Full-text available
Unlabelled: Malassezia commensal yeasts are associated with a number of skin disorders, such as atopic eczema/dermatitis and dandruff, and they also can cause systemic infections. Here we describe the 7.67-Mbp genome of Malassezia sympodialis, a species associated with atopic eczema, and contrast its genome repertoire with that of Malassezia globo...
Data
Comparison of tetrapolar, bipolar, and pseudobipolar mating systems in basidiomycete fungi. In the tetrapolar mating type paradigm, the MAT loci (HD and P/R) are located on separate chromosomes and multiple HD and at least two P/R alleles are observed, resulting in multiple possible mating types. In the bipolar mating type paradigm, the MAT loci ar...
Data
Full-text available
Conservation of REC8/RAD21 homologs. Sequences were aligned using SeaView (108), and trees were constructed from conserved regions at the N and C termini using the PhyML algorithm in SeaView. Sequences from basidiomycetes are highlighted in green, and the M. globosa gene is shown in bold. The RAD21 gene model from M. sympodialis (MSY001_15220) is n...
Data
List of M. sympodialis isolates.
Data
Full-text available
Supplemental methods for homology-based and de novo identification of specific genes, expression and gene deletion of the Mala s 1 ortholog in U. maydis, linkage analysis of M. sympodialis MAT loci, mating assays, and mating type identification. Download
Data
Full-text available
A single β-glucosidase of class 3 in the genomes of Malassezia species. Gene tree of basidiomycete β-glucosidases of class 1 (GH1) and 3 (GH3), rooted with the ascomycete Aspergillus nidulans GH1. For each species, the taxonomic name (Phanerochaete chrysosporium, Coprinopsis cinerea, Schizophyllum commune, Cryptococcus neoformans, Ustilago maydis,...
Data
Full-text available
Expression and deletion analysis of um04915 in U. maydis. (A) Quantitative real-time PCR results at 12, 24, 48, and 96 h postinfection of 7-day-old maize plants with strain SG200. Mean expression values are displayed relative to the expression in axenic culture (YEPSL medium). Error bars indicate standard deviations of mean expression values. (B) V...
Data
Full-text available
Gene tree of Mala s 7-like proteins in Malassezia. The Mala s 7-like proteins from M. globosa (MGL_0968, JX857443, and MGL_2673) and from M. sympodialis (7a, 7b, 7c, and 7d) form well-supported (bootstrap values on a scale of 1 to 100) separate groups. The previously published allergen sequence for Mala s 7 (39) corresponds to 7a. Copies coding for...
Data
Full-text available
Alignment of B locus alleles in M. sympodialis isolates. The nucleotide sequences of the B (HD) locus between isolates ATCC 42132, ATCC 44340, and KS024 (see Table S2 in the supplemental material) were aligned using ClustalW (92). Yellow and gray regions represent bW and bE genes, respectively. The homeodomain is highlighted with a solid red line,...
Data
M. sympodialis proteins involved in cell wall biosynthesis and remodeling and their homologs in M. globosa and U. maydis.
Data
Conservation of genes associated with mating and meiosis in fungi.
Article
Full-text available
Malassezia commensal yeasts are associated with a number of skin disorders, such as atopic eczema/dermatitis and dandruff, and they also can cause systemic infections. Here we describe the 7.67-Mbp genome of Malassezia sympodialis, a species associated with atopic eczema, and contrast its genome repertoire with that of Malassezia globosa, associate...
Article
It has long been known that women lose satisfaction with their hair with ageing. Our data show that caucasian women perceive a decrease in hair amount in their mid 40s with a further decrease in the mid to late 50s, which leads to this dissatisfaction. Neither loss of density (hairs per cm(2) ) nor shaft diameter alone can fully account for this pe...
Article
Androgenetic alopecia affects both men and women. In men it produces male pattern hair loss with bitemporal recession and vertex baldness. In women it produces female pattern hair loss (FPHL) with diffuse alopecia over the mid-frontal scalp. FPHL occurs as a result of nonuniform hair follicle miniaturization within follicular units. Diffuse alopeci...
Article
Many of today's treatments associated with 'thinning hair', such as female pattern hair loss and telogen effluvium, are focused on two of the key aspects of the condition. Over-the-counter or prescription medications are often focused on improving scalp hair density while high-quality cosmetic products work to prevent further hair damage and minimi...
Chapter
Women who undergo menopause have a cessation of ovarian estrogen production. This dramatic hormonal alteration is known to have significant effects on the skin and cutaneous appendages. As our understanding of the molecular and hormonal controls on the folliculo-sebaceous unit has grown, there has been renewed interest in the role of estrogens in m...
Chapter
The recent sequencing of the genomes of dandruff-associated basidiomycetous yeasts, Malassezia globosa and Malassezia restricta, disclosed that the M. globosa genome is among the smallest for a free-living fungus. M. globosa produces a similar set of secreted hydrolases as the human pathogen Candida albicans. Although phylogenetically more closely...
Article
Auteur(s) : Rodney D Sinclair1, James R Schwartz2, Heather L Rocchetta2, Thomas L Dawson Jr3, Brian K Fisher3, Knut Meinert4, Elizabeth A Wilder3 1Department of Dermatology, St. Vincent’s Hospital Melbourne, University of Melbourne, P.O. Box 2900 Fitzroy Victoria Australia 3065 2Sharon Woods Innovation Center, The Procter & Gamble Company, Cincinna...
Article
Full-text available
Dandruff and seborrheic dermatitis (D/SD) share an etiology dependent upon three factors: sebum, microbial metabolism (specifically, Malassezia yeasts), and individual susceptibility. Advances in microbiological and analytical techniques permit a more detailed understanding of these etiologic factors, especially the role of Malassezia. Malassezia a...
Article
Full-text available
Fungi in the genus Malassezia are ubiquitous skin residents of humans and other warm-blooded animals. Malassezia are involved in disorders including dandruff and seborrheic dermatitis, which together affect >50% of humans. Despite the importance of Malassezia in common skin diseases, remarkably little is known at the molecular level. We describe th...
Article
Full-text available
Dandruff and seborrheic dermatitis (D/SD) are common hyperproliferative scalp disorders with a similar etiology. Both result, in part, from metabolic activity of Malassezia globosa and Malassezia restricta, commensal basidiomycete yeasts commonly found on human scalps. Current hypotheses about the mechanism of D/SD include Malassezia-induced fatty...