Journal of Cosmetics, Dermatological Sciences and Applications, 2013, 3, 26-34
http://dx.doi.org/10.4236/jcdsa.2013.33A1004 Published Online September 2013 (http://www.scirp.org/journal/jcdsa)
Mutations with Hair Shape Phenotypes Abnormalities—
The Morphogenetic Waves and Related Diseases
Junmin Wang1, Guannan Wang2, Jintao Zhang1*
1Laboratory Animal Center, Zhengzhou University, Zhengzhou, China; 2College of Life Sciences, Henan Agricultural University,
Zhengzhou, China.
Received June 10th, 2013; revised July 8th, 2013; accepted July 16th, 2013
Copyright © 2013 Junmin Wang et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Hair morphology is one of the most conspicuous features of human variation. The hair follicle has attracted significant
attention as a model for the investigation of diverse biological problems. Whereas, very little is known about the genes
influencing the morphology and structure of the hair shaft. Curly hair is very common character of hair phenotypes of
human, while most congenital curl occurs owing to genetic factors and some are closely related with genetic diseases.
This review highlights current related genes reported affecting hair curliness and human diseases which are due to gene
mutations.
Keywords: Waved Hair; Curly Hair; Gene Mutations; Diseases
1. Introduction
A mammal’s pelage is generally one of its first notice-
able attributes and is aesthetically pleasing. Moreover,
the skin is an essential organ which protects the organism
from invasion of pathogens and chemicals and prevents
the escape of liquids and nutrients [1]. Its ectodermal
appendages, such as hair, feather and tooth, are attractive
models for understanding the mechanisms underlying
epithelial mesenchymal interactions [2].
Hair is composed of terminally differentiated, dead
keratinocytes (trichocytes), which are compacted into a
fibre of amazing tensile strength, the hair shaft. Hair
morphogenesis and epidermal development are orches-
trated by an array of cytokines and growth factors [3].
The presence of hair is characteristic for mammals, in
which it exerts a wide range of tasks, including physical
protection, thermal insulation, camouflage, dispersion of
sweat and sebum, sensory and tactile functions, and so-
cial interactions [4]. In human society, hair is of enor-
mous, psychosocial importance, and many human dis-
eases are associated with abnormalities in hair follicle
morphogenesis, cycling, and structure.
A hair grows from the papilla and with the exception
of that point of generation is made up of dead, cornified
cells. It consists of a shaft that projects above the skin,
and a root that is imbedded in the skin. Its basic compo-
nents are keratin (a protein), melanin (a pigment), and
trace quantities of metallic elements [5]. These elements
are deposited in the hair during its growth and/or ab-
sorbed by the hair from an external environment. After a
period of growth, the hair remains in the follicle in a
resting stage to eventually be sloughed from the body. As
the place of origin of the hair, the structural change of
hair follicle could directly cause the change of hair phe-
notype [6,7].
The hair follicle represents an attractive experimental
system because of its accessibility, dispensability, and
self-renewal capacity. Owing to its complex but highly
organised architecture, this mini-organ can serve as an
excellent model for investigating aspects of stem cell
biology, cell lineage specification, cell differentiation,
patterning processes, and cell-cell interactions [8,9]. In
addition, hair follicles and shafts are of significant cos-
metic relevance. The follicle provides the source for hair
production and, thus, eventually determining appearance
by affecting the hair shaft’s structure and shape. Hair
features are not only affected by the follicle’s capacity to
give rise to a normal shaft but also by the so-called hair
growth cycle which controls the periodic growth and
shedding of hair.
Human hair is one of most keratinous fibres. There are
various fibre shapes in human hair and it is commonly
*Corresponding author.

Mutations with Hair Shape Phenotypes Abnormalities—The Morphogenetic Waves and Related Diseases 27
accepted that the curliness of hair fibres is roughly clas-
sified by their ethnic origin in the three major ethnic
groups: African hair which has a strong curl shape, Cau-
casian hair which has a moderately waved shape, and
Asian hair which is apt to have a comparatively straight
shape [10]. The corresponding difference in the internal
nanostructure, however, still remains unrevealed.
The structured pattern of hair is determined by their
length, width, and shape. Whereas the prototype hair is
straight, hair can adopt different shapes owing to bend-
ing. In principle, bending could be achieved by diverse
means. Differences in cell proliferation on opposite sides
of the hair follicle would inevitably give rise to hair cur-
vature [11]. Understanding the factors that contribute to
the curly morphology of human hair is important for an-
thropological and physiological studies. According to a
recent report, hair curling in man is a consequence of
different proliferation rates within the hair follicle that
appear to be reflected by the shape of the follicle [12,13].
This correlation is reminiscent of the potential link be-
tween follicle and hair size.
Curliness has commonly been assessed using words
such as straight, wavy, curly and frizzy, a variety of at-
tributes of subjective nature with no clear definition and
limits [14]. Curly hair is very common character of hair
phenotypes of human, which is caused by many reasons.
Most congenital curl occurs as the result of genetic fac-
tors and some are closely related with genetic diseases.
Genetic analyses of common diseases in humans have re-
vealed that gene mutations are involved in diseases. Ge-
nome sequencing projects of various mammalian species
followed by comparative genome analyses have revealed
that a large number of genes are shared among species.
Thus, it is thought that mutations found in model animals
and animals carrying such mutations are of large signifi-
cance in studying hair growth regulation and the rela-
tionship with some hereditary diseases.
2. The Curly Hair-Specific Genes
Several genetic alterations with different follicular local-
izations of the primary aberration give rise to curly or
wavy hair and curly pelage is an easily recognized trans-
species coat anomaly, moreover, several detailed studies
in various mammalian species. In mice, Caracul (Ca)
mice, a dominant mutation mapped to mouse chromo-
some 15 and missense point to a single amino acid ex-
change at the beginning of the a-helical rod domain of
Krt71, a few amino acids apart from four identified Ca
alleles possess curly hair and vibrissae after birth [15].
two novel krt 71rco12 and rco13 mutant mice, displaying a
wavy pelage and curly vibrissae, have been identified as
missense point mutations in the first exon of the krt
71gene [16]. In rat, the autosomal dominant Rex (Re)
mutation in the Krt71 gene, on chromosome 7, causes
wavy body hair in Re/+ and body hair loss in Re/Re rats
after the first molt. The homozygote exhibits more waved
pelage and smaller body size and histological analysis of
1-month-old mice revealed bent hair follicles and fragile
hair shafts, vibrissae of the homozygote are more
strongly curled than those in the heterozygote [17,18].
Recently, genome-wide single-nucleotide polymor-
phism (SNP) association studies led to candidate gene
screening for the curly/wavy coat of the portuguese water
dog. A SNP in keratin-71 (KRT71) was shown to cause a
nonsynonymous mutation in exon 2, having been re-
cently identified in curly hair in dogs [19]. In cat, a com-
plex sequence alteration of the KRT 71 gene, also caus-
ing a splice variation, was identified in the Devon Rex
breed with curly coats [20]. In cattle, an autosomal re-
cessive form has been described in Hereford cattle, an
8-bp deletion mutation occurring in exon 1 causes an
early truncated KRT71 protein resulting in a curly-hair
coat [21]. More gene mutations affecting the morphoge-
netic waves are showed in the Table 1.
3. Hair Curliness-Related Inherited Diseases
3.1. Pseudofolliculitis Barbae (PFB)
Pseudofolliculitis barbae, a common human hair disorder,
showing a chronic, irritating, and potentially disfiguring
condition that develops as a result of attempts to elimi-
nate hair from the beard area, usually by shaving [56].
The disease is, however, not gender-specific, nor re-
stricted to the face, but can occur in any hairy skin region
upon regular shaving or other means of hair removal [57].
Compared to Caucasian males, black males are distinctly
more susceptible to developing PFB due to their genetic
predisposition for strongly curved hairs and the study
showed that incidence rate of the disorder can affect up
to 1 out of every 5 Caucasian individuals while it occurs
much more commonly in black persons [58]. The muta-
tion analysis of K75 and the IRS keratins in a three-gen-
eration Caucasian family whose male members suffered
from relatively severe PFB symptoms revealed that af-
fected males exhibited a heterozygous point mutation in
the KRT75 gene. The mutation was also present in a fe-
male member of the family, however, this individual did
not shave nor remove hairs by other means, and she was
free of symptoms. Clinical features include the appear-
ance of inflammatory papules and pustules. Molecular
analysis in a family study and a large-scale investigation
of randomly sampled PFB-affected and -unaffected indi-
viduals showed that an unusual single-nucleotide poly-
morphism, which gives rise to a disruptive Ala12Thr
substitution in the 1A a-helical segment of the compan-
ion layer-specific keratin K6hf of the hair follicle, is par-
tially responsible for the phenotypic expression and
represents an additional genetic risk factor for PFB [59].

Mutations with Hair Shape Phenotypes Abnormalities—The Morphogenetic Waves and Related Diseases 28
Table 1. Genes mutations causing the morphogenetic waves.
Gene Name Symbol Synonyms ChrCharacteristic Reference
Adam 17
a disintegrin and
metallopeptidase domain 17;
mutation 1, Bruce Beutler
Adam17m1Btlr Waved X 12 Wavy coat [22]
Adam 17
a disintegrin and
metallopeptidase domain 17;
waved with open eyelids
Adam17woe
Adam17delta252-281,
Adam17deltaexon7,
Adam17T265M, wa3
12 Wavy fur [23, 24]
Areg amphiregulin; targeted
mutation 1, David C Lee Aregtm1Dle AR- 5
Egf
epidermal growth factor;
targeted mutation 1, David C
Lee
Egftm1Dle 3
Wavy hair and curly vibrissae
due to HF orientation and
alignment problems.
[25]
cub curly bare cub 11
The mice with a single dominant
allele show wavy hair. [26]
Dicer1
dicer 1, ribonuclease type III;
targeted mutation 1, Sarah E
Millar
Dicer1tm1Smr DicerflEx22-23 Dicerflox 12
Drosha
drosha, ribonuclease type III;
targeted mutation 1, Dan R
Littman
Droshatm1Litt DroshaF, DroshaflEx9,
Droshalox 15
External hair becomes wavy
between P12 and P14 in
doxycycline-treated mice
[27]
Egfr epidermal growth factor
receptor ; dark skin 5 EgfrDsk5 11
Slight wave to the coat becomes
less apparent with age [28]
Egfr
epidermal growth factor
receptor; targeted mutation 1,
David W Threadgill
Egfrtm1Dwt Egfrfl 11
Egfrf/f, K14-Cre mice at 3 months
of age display wavy coat [29]
Egfr epidermal growth factor
receptor; velvet EgfrVel 11 The first coat is wavy [30]
Egfr epidermal growth factor
receptor; waved 2 Egfrwa2 wa2, wa-2, waved2 11
Aggregation chimeras between
Egfrwa2/Egfrwa2 and +/+ embryos
result in a patchy distribution of
waved and normal hair
[31]
Egfr epidermal growth factor
receptor; waved 5 EgfrWa5 GENA 239 11
The first coat is described as
wavy and subsequent coats are
scruffy in appearance.
[32]
Ets2
E26 avian leukemia oncogene
2, 3' domain; targeted mutation
1, Robert G Oshima
Ets2tm1Rgo Ets2db
ets2db1 16
Wavy hair, curly vibrissae,
abnormal HF shape and
arrangement.
[33]
Ets2
E26 avian leukemia oncogene
2, 3' domain; targeted mutation
5.1, Robert G Oshima
Ets2tm5.1Rgo Ets2fl
Ets2LoxP 16 Ets2fl/fl adult has a waved hair phenotype [34]
Foxe1 forkhead box E1; targeted
mutation 1, Roberto Di Lauro Foxe1tm1Rdl Titf2- 4
On grafted skin, the hair coat
appears kinky. [35]
Hag hague Hag 15
Curly hair is more obvious in
young mice [less than 2 months
of age]
[36]
Krt25 keratin 25; rex Krt25Re Re 11
Beginning at 1 month of age
pelage is wavy compared to
wild-type mice but this waviness
becomes weaker as mice age
[37]
Krt71 keratin 71; caracul Rinshoken Krt71Ca-Rin 15
Hair is wavy and points in all
directions. After 4 weeks, the
wavy hair is less apparant but
mice maintain a plush-like
appearance
[15]
Krt71 keratin 71; caracul Krt71Ca Ca 15
Curved vibrissae and wavy hair
until about 4 weeks of age. [38]
Krt71 keratin 71; Martin Hrabe de
Angelis reduced coat 12 Krt71Mhdarco12 Krt71Rco12, rco12,
reduced coat 12
Krt71 keratin 71; Martin Hrabe de
Angelis reduced coat 13 Krt71Mhdarco13 Krt71Rco13, rco13,
reduced coat 13
15
Curly hair is visible by P10 and
becomes less pronounced by 3
months of age
[39]
Krt71 keratin 71; RIKEN Genomic
Sciences Center (GSC), 689 Krt71Rgsc689 Krt2-6g1Rgsc, M10068915
Curl of coat was prominent at
early stage (before 6 weeks) but
unremarkable after 8 weeks
[15]

Mutations with Hair Shape Phenotypes Abnormalities—The Morphogenetic Waves and Related Diseases 29
Continued
Liph lipase, member H; targeted
mutation 1, Junken Aoki Liphtm1Aoki PA-PLA1alpha- 16 Wavy hair cuticle [40]
Notch1 notch 1; targeted mutation 2,
Raphael Kopan Notch1tm2Rko fN1, N1f, NICD1fl, Notch1flox, Notch1tm1Shn 2 Regions of wavy hair that have a twisted, knotted morphology [41]
Ppp1r13l
protein phosphatase 1,
regulatory (inhibitor) subunit
13 like; waved 3
Ppp1r13lwa3 7
Curly hairs. Thinner hair shafts.
At P8, abnormal shape and
orientation of HFs.
[42]
Ppp1r13l
protein phosphatase 1,
regulatory [inhibitor] subunit
13 like; waved with open
eyelids 2
Ppp1r13lwoe2 7
Beginning around P14 and
remaining throughout life [25]
Sgk3
serum/glucocorticoid regulated
kinase 3; fuzzy Iasi congenital
atrichia
Sgk3fz-ica 1
Sparse hair,curly vibrissae,
abnormal hair shaft morphology,
abnormal hair cycle
[43]
Sgk3
serum/glucocorticoid regulated
kinase 3; fuzzy Mark D
Fleming
Sgk3fz-Mdf 1 [44]
Sgk3
serum/glucocorticoid regulated
kinase 3; targeted mutation 1,
David Pearce
Sgk3tm1Dpea Sgk3- 1
Early hair follicle development is
normal, however by P4 the
follicles have failed to enlarge
and migrate deep into the
subcutis
[45]
Stk11
serine/threonine kinase 11;
targeted mutation 1.1, Ronald
DePinho
Stk11tm1.1Rdp Lkb1lox 10 Adult hair is wavy [46]
Tg[EGFR]0Jlj transgene insertion 0, Jose Luis
Jorcano Tg[EGFR]0Jlj K5-HERCD-533, T0
Dominant negative. Short and
waved hairs and curly whiskers.
Degeneration and destruction of
HFs in 3 to 4 weeks old mouse.
[47]
Tg[Notch1]1Anc transgene insertion 1, Angela
M Christiano Tg[Notch1]1Anc
Wavy hairs and short, curly
vibrissae. Defect in
differentiation of the inner root
sheath. Persistence of inner root
sheath remnants in later stage of
the hair cycle.
[48]
Tg[Notch1]A5Rko
transgene insertion A5,
Raphael Kopan Tg[Notch1]A5Rko MHKA-NotchdeltaE
Decreased curvature of zigzag
hairs [49]
Tgfα
transforming growth factor
alpha; targeted mutation 1,
Ashley R Dunn
Tgfαtm1Ard Tgfαlpha - 6 Attenuated slightly with age [50]
Tgfα
transforming growth factor
alpha; targeted mutation 1,
University of North Carolina
Tgfαtm1Unc TGFalpha-, Tgfatm1Dcl 6
Between 2 - 4 weeks of age the
coat develops a wavy
appearance.
[51]
Tgfα transforming growth factor
alpha; waved 1 Tgfαwa1 wa-1, waved 6
Wavy hair is obvious at 10 days
of age, extreme waviness of the
first coat is lost in later hair
generations but the coat never
looks normal
[52]
Tgm3
transglutaminase 3, E
polypeptide; targeted mutation
1, Susan John
Tgm3tm1Sjo 2
Wavy hair is most obvious in the
first four weeks of life [53]
Trpv3
transient receptor potential
cation channel, subfamily V,
member 3; targeted mutation
1.2, David E Clapham
Trpv3tm1.2Clph V3 KO 11
HFs were gently curved and
pointed in different directions
with variable angles.
[54]
wal waved alopecia wal 14
At 2 weeks of age the hair is
curly [55]

Mutations with Hair Shape Phenotypes Abnormalities—The Morphogenetic Waves and Related Diseases 30
3.2. Tricho-Dento-Osseous (TDO)
Tricho-dento-osseous syndrome is a rare human genetic
disorder first distinguished by Lichtenstein et al., in 1972
[60]. It is a highly penetrant autosomal dominant trait
characterized by curly kinky hair in infancy, enamel hy-
poplasia, taurodontism, thickening of cortical bones and
variable expression of craniofacial morphology [61].
Diagnostic criteria are based on the generalized enamel
defects, severe taurodontism especially of the mandibular
first permanent molars, an autosomal dominant mode of
inheritance, and at least one of the other features (i.e.,
nail defects, bone sclerosis, and curly, kinky or wavy hair
present at a young age that may straighten out later).
Kinky or tightly curled hair at birth may be a characteris-
tic and distinguishing feature in many families and aid in
diagnosing TDO from hypomaturation-type amelogene-
sis imperfecta [62,63]. TDO syndrome is considered the
ectodermal dysplasia with a high penetrance even if the
individual signs and symptoms can be present in variable
intensities. Genetic studies have shown a mutation in the
DLX3 gene on chromosome 17q21 and a 4 bp deletion in
the DLX3 gene associated with TDO, which has also
been identified [64]. Some families have been reported to
have wavy hair or curly hair at birth that straightened out
a few years later [65-67]. Seow [68] reported that the hair
defects may vary among affected members of the same
family. Mayer et al. [62] reported that an 8-year-old girl
with TDO syndrome had uncombable hair, enamel hy-
poplasia and enlarged pulp chambers of the molar teeth.
Electron microscopic examination of the curly hair
showed a flattened hair shaft with longitudinal grooves.
3.3. Oculo-Dento-Digital Dysplasia (ODDD)
Oculo-dento-digital dysplasia is a rare autosomal domi-
nant congenital disorder caused by mutations in con-
served domains of the gap junction alpha 1 gene (GJA1
or Connexin 43 (CX43)) located on chromosome 6q21-
q23.2 with two exons separated by an 11-kb intron [69].
Abnormalities observed in ODDD affect the eye, denti-
tion, and digits of the hands and feet [70]. Patients pre-
sent with a characteristic facial appearance, narrow nose,
and hypoplastic alae nasi. Neurological problems are
known to occur as well as conductive hearing loss, car-
diac defects, and anomalies of the skin, hair, and nails.
Curly/kinky hair with features of early trichorrhexis
nodosa was identified in a 13 years old girl with ODDD
[71], this in accord with the observation by Kjaer et al.,
who found curly hair in seven out of nine affected sub-
jects harboring a mutation in the Cx43 gene in a Danish
family over five generations [72].
3.4. Woolly Hair (WH)
Woolly hair is a group of hair shaft disorders, which re-
fers to an abnormal variant of fine, tightly curled hair that
often exhibits decreased pigmentation. Hutchinson et al.
[73] classified woolly hair into 3 variants: woolly hair
nevus, autosomal dominant hereditary woolly hair, and
autosomal recessive familial woolly hair. Since then, WH
has also been observed in association with several ge-
netic conditions, such as Naxos disease and Carvajal
syndrome, both of which are characterized by cardio-
myopathy, palmoplantar keratoderma, and WH, and are
caused by mutations in the plakoglobin [74] and desmo-
plakin [75] genes, respectively. Furthermore, most nota-
bly is Noonan syndrome and cardiofaciocutaneous (CFC)
syndrome. Andy J. Chien described a family with woolly
hair and ulerythema ophryogenes spanning four genera-
tions, which have been associated with Noonan syn-
drome and CFC, and he found that this family did not
exhibit any of the other findings characteristic of either
Noonan syndrome or CFC, similar to a previously de-
scribed pedigree with hereditary woolly hair [76]. In ad-
dition to these syndromes, WH without associated find-
ings (non-syndromic WH) has also been described [77].
4. Acknowledgements
This publication was supported by grants from China
Natural Science Foundation (#31071923).
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