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Title:
Identification of mutation in connexin30 gene, GJB6 in a Chinese family with congenital
nail clubbing and alopecia
Type: Brief Communication
Running title: GJB6 mutation in congenital disorder
Authors:
Mousumi Tania1 MS
Zhimin Xiong1 MS
Lina Lu1 MS
Shuanglin Liu2 MD
Kun Xia1,* PhD
Zhengmao Hu1,* PhD
Funding source: National Basic Research Program of China (2012CB517902) and National
Natural Science Foundation of China (81070081)
1
Affiliations:
1State
key lab of medical genetics, Central South University, Changsha, Hunan, China,
2Maternity
and child health hospital of Liuyang, Hunan, China
*For correspondence: Dr. Zhengmao Hu, E-mail: [email protected], Tel.: +86 731
84805357; fax: +86 731 84478152 and *Dr. Kun Xia, State Key Laboratory of Medical
Genetics, Central South University, No. 110 Xiangya Road, Changsha City, Hunan 410000,
China, E-mail: [email protected], Tel.: +86 731 84805357; fax: +86 731 84478152
(Before
publication
correspondence
is
requested with
Mousumi
Tania
(e-mail:
[email protected]
2
Abstract
Mutation in the gap junction beta 6 (GJB6) genes has been reported to be associated with an
autosomal dominant disorder, characterized by congenital nail clubbing, alopecia and
palmoplantar keratoderma. We have investigated the genetic mutation in GJB6 in an affected
Chinese family. The whole coding region of GJB6 was amplified by PCR and sequenced.
Sequencing identified a heterozygous missense mutation (G11R) in GJB6 gene of affected
individuals but not in normal healthy control. Our report confirms G11R missense mutation
in GJB6 gene, responsible for the congenital disorder characterized with nail clubbing and
alopecia in Chinese population.
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Dominant and recessive mutations in the GJB6 gene encoding connexin30 (Cx30) are
associated with a variety of human inherited diseases primarily affecting the epidermis, hair,
nail, and/or the inner ear. The disorder characterized by congenital nail clubbing and alopecia
has long been considered as a group of rare, autosomal dominant and obscure disorders1.
Congenital nail clubbing is a distinct rare genodermatosis entity, characterized by shortened
of the nail plate, loss of the cuticle and terminal segments of the fingers and toes, resulting
from the swelling of the soft tissue of the terminal phalanx of a digit with subsequent loss of
the normal angle between the nail and the nail bed. Also, symmetric, hard, tender,
yellow-brown colored keratotic plaques (palmoplantar keratoderma) developed over the
entire palms and sole. Congenital alopecia is clinically characterized by shedding of normal
scalp hair with failure to re-grow, sparse eyebrow and eyelashes, and lack of secondary
axillary, pubic or body hair and, in few cases, hearing impairment has also been reported2.
There are genetic evidences that mutation in the gap junction beta 6 (GJB6) is related to these
disorders3. In this study, we have investigated a Chinese family affected with congenital nail
clubbing and alopecia, and palmoplantar hyperkeratosis showing no evidence of any other
abnormality.
A five-generation Chinese family presenting nail clubbing and alopecia with four affected
and two unaffected members was identified in Hunan Province, China. The pedigree analysis
provided strong evidence of autosomal dominant inheritance and it accounted for all of the
affected persons being heterozygous for a mutant allele (Fig. 1). All the affected patients had
the similar clinical presentation. At birth, nail clubbing was noticed but alopecia was noticed
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at six years old. Physical examination revealed loss of scalp hair, eyelashes, eyebrows and
body hair on other parts of the body (Fig. 2). Before the study, informed consent was
obtained from all the patients and controls. Genomic DNA from peripheral blood was
extracted according to phenol-proteinase-K method. The entire coding sequence of human
GJB6 was amplified by PCR using the following balanced primer pairs: (1)
5’-agactagcagggcagggagt-3’ (forward) and 5’-GGAAAAAGATGCTGCTGGTG-3’ (reverse),
(2)
5’-CCTCCAGCTGATCTTCGTCT-3’
(forward)
and
5’-GGTTGGTATTGCCTTCTGGA-3’ (reverse) and HotStar Taq DNA polymerase. Thermal
cycling was performed using a thermal cycler (Applied Biosystems). After the amplification,
PCR products were sequenced biderctionally on an ABI-PRISM3100 automated sequencer
(Applied Biosystems). All the sequencing results were assembled, analyzed and compared to
the corresponding wild-type sequences using the SeqMan II program of the Laser gene
package (DNA STAR Inc., Madison, WI).
Sequence analysis identified a single nucleotide change 31(G→A) in the N-terminal region of
GJB6 gene’s exon leading to the substitution of one amino acid on the N-terminal tail of the
protein (glycine is substituted by arginine: G11R) in affected individuals (Fig. 3). None of the
deletions, insertions or missense mutations described here was found in normal individuals.
In this study, we report that the affected individuals of this Chinese family presented a
missense mutation (31G→A) in the coding region of the GJB6 gene, which codes for the gap
junction protein, Cx30. Cx30 is a member of the connexin protein family which forms
channels called gap junctions that permit the transport of nutrients, ions and signaling
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molecules between neighboring cells4, thus coordinating metabolic activities in multi-cellular
tissues. Genetic approaches have uncovered a still growing number of mutations in connexins
related to human diseases including deafness, skin disease, peripheral and central
neuropathies, cataracts, or cardiovascular dysfunctions5. GJB6 gene mutations probably cause
abnormal transport activity through the gap junctions. At least three different amino acid
substitutions have been identified in Cx30 gene: Gly 11 to Arg (G11R) and Ala 88 to Val
(A88V) and Val 37 to Glu (V37E)1. We are reporting here (G11R) mutation in congenital nail
clubbing, alopecia and palmoplantar keratoderma in a Chinese family. Mutation at this
position has been identified in some other studies in European and Chinese individuals with
these phenotypes1,4. To confirm the mutation pattern and position, investigation with more
sample volume from different region of the world is recommended. It is expected that the
identification of GJB6 mutations will enable a rapid molecular diagnosis, and may reveal the
pathological mechanisms, which in future will help to find out treatment of this rare genetic
disorder.
Acknowledgments
This study is funded by the National Basic Research Program of China (2012CB517902) and
National Natural Science Foundation of China (81070081). We are thankful to the patients
for supporting our study. We are thankful to Chinese Scholarship Council for providing
financial support to the 1st author.
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References
1.
Zhang XJ, Chen JJ, Yang S, Cui Y, Xiong XY, He PP, et al. A mutation in the
connexin 30 gene in Chinese Han patients with hidrotic ectodermal dysplasia. J
Dermatol Sci 2003; 32: 11-17.
2.
Yildirim M, Yorgancilar E, Gun R, Topcu I. Ectodermal dysplasia: otolaryngologic
evaluation of 23 cases. Ear Nose Throat J 2012; 91: E28-33.
3.
Lamartine J, Munhoz Essenfelder G, Kibar Z, Lanneluc I, Callouet E, Laoudj D, et al.
Mutations in GJB6 cause hidrotic ectodermal dysplasia. Nat Genet 2000; 26: 142-144.
4.
Smith FJ, Morley SM, McLean WH. A novel connexin 30 mutation in Clouston
syndrome. J Invest Dermatol 2002; 118: 530-532.
5.
Zoidl G, Dermietzel R. Gap junctions in inherited human disease. Pflugers Arch 2010;
460: 451-66.
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Figure legends
Figure 1. Pedigree analysis of the Chinese family with autosomal dominant nail clubbing and
alopecia, taken in this investigation. Normal individuals are shown as clear circles (female) or
squares (male), and affected individuals are shown as solid symbols. Deceased individuals
are shown with a slash. The arrow indicates the proband.
Figure 2. Phenotypes of the studied individuals: (a) Thickened, striated, often discolored
fingers’ nails; (b) short, thin and brittle toes’ nails; (c) hyperkeratosis of the palms; (d) shows
alopecia; (e) virtually absent eyebrows and eyelashes; (f) lack of body hairs in lower leg
portion.
Figure 3. Partial sequence chromatographs of wild type GJB6 31G (upper panel) and the
heterozygous missense mutation 31G→A identified in all patients (lower panel).
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