Dr. Xue Zhang, who is associated with the Peking Union Medical College Hospital (PUMCH) in Beijing, China, and fellow colleagues found that chemical levels of the HR gene must be maintained at a certain level in order to prevent hair loss in children afflicted with the a rare form of hair loss called Maria Unna Hereditary hypotrichosis (MUHH), also called congenital atrichia.
They specifically found that problems in the gene U2HR cause MUHH.
The baldness disease is named after German dermatologist Maria Unna, who first identified the problem (calling it hypotrichosis congenital hereditaria) in 1925 (Unna, M: Uber Hypotrichosis Congenita Hereditaria. Dermatol Wochenschr 81:1167–1178, 1925) after reporting the problem in 27 individuals in northern Germany.
The Chinese researchers state that in the abstract to their paper “Marie Unna hereditary hypotrichosis (MUHH) is an autosomal dominant form of genetic hair loss.”
It has been known for about a decade that HR (hairless homolog) genes are responsible for congenital atrichia. These researchers have identified the mutation of the gene.
In congenital atrichia, babies are born with little or no hair on their heads. During the first-year of life, infants gradually lose their course and thin hair through puberty, and it never returns.
MUHH affects both men and women. In adulthood, MUHH patients do not normally have armpit and pubic hair, along with not having eyebrows or eyelashes.
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The paper summarizing the work of Dr. Zhang, Yang Liu, Yi8ming Xu, Yiwei Zhao, and colleagues is entitled “Loss-of-function mutations of an inhibitory upstream ORF in the human hairless transcript cause Marie Unna hereditary hypotrichosis.”
The found that U2HR (found on chromosome 8) is a critical switch in the process deciding whether children have this balding disease or not.
U2HR controls a tiny peptide that, itself, affects a known protein called the human hairless monolog (HR), which is important for the growth and regeneration of hair follicles.
They stated, “In a large Chinese family carrying MUHH, we identified a pathogenic initiation codon mutation in U2HR, an inhibitory upstream ORF in the 5' UTR of the gene encoding the human hairless homolog (HR). U2HR is predicted to encode a 34–amino acid peptide that is highly conserved among mammals.”
The researchers studied eighteen families from several ancestral backgrounds. They “... identified a range of defects in U2HR, including loss of initiation, delayed termination codon and nonsense and missense mutations. Functional analysis showed that these classes of mutations all resulted in increased translation of the main HR physiological ORF.”
They concluded, “Our results establish the link between MUHH and U2HR, show that fine-tuning of HR protein levels is important in control of hair growth, and identify a potential mechanism for preventing hair loss or promoting hair removal.
The discovery should help to spur development of drugs that could prevent MUHH and it also offers hope that baldness may someday be cured.