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Deaf awareness week 2017 is a cause for celebration

A hand held next to an earHearing loss affects one in six people in the UK and around 360 million people worldwide. This year, the UK Council on Deafness is co-ordinating Deaf Awareness Week from 15-21 May 2017, with a theme of ‘celebration’ of collaborative efforts to raise awareness, provide services for affected individuals and advance research into prevention of hearing loss. Joining the celebration of deafness-related research, Disease Models & Mechanisms (DMM) is pleased to present a selection of articles on disorders affecting the ear and hearing.

Models for a common childhood disease

Otitis media (OM), or middle ear inflammation, is one of the most common infectious diseases in childhood, with up to 80% of all children affected at least one by the age of three years. Although most children suffer no long-term effects, complications of OM are a leading cause of preventable hearing loss, particularly in the developing world. The mechanisms behind the disease remain poorly understood as the functional changes to the affected middle ear are complex, but researchers have found links to epithelial abnormalities. Research is further hampered by the lack of a well-characterised in vitro models of the middle ear epithelium. In a recent DMM paper, Bingle and colleagues report the development of an in vitro otopathogenic infection model of mouse middle ear epithelium to allow investigations into the epithelium. Mouse models have also proven to be important to explore the complex causes behind OM, as reflected by research in DMM. For example, focusing on one of the bacteria associated with acute OM, Haemophilus influenza, Hood and colleagues developed a novel susceptible mouse model to allow testing of vaccine and antibiotics for prevention or treatment of middle ear infections.

Hair cell degeneration as a cause of deafness

Whole-mount preparation of mouse outer hair cells

Karen Steel began studying the genetics of deafness in mutant mouse lines serendipitously, but has forged an impressive career in the field. Degeneration of the sensory hair cells of the inner ear was previously thought to be the primary cause of deafness. However, Karen’s research was among the first to identify that this degeneration is in fact a secondary feature of deafness, brought about by defects in the hair cells themselves, or some other part of the auditory apparatus. Revisit the classic DMM interview with Karen in which she reveals the vital role of mutant lines in understanding the genetics of deafness, and why she believes passionately in open science and sharing of resources.

In addition to the inner ear cells studied by Karen, mammalian cochlear outer hair cells also lack the ability to regenerate after damage, which can lead to irreversible sensorineural hearing loss. Mitogen-activated protein kinase, or MAP3K1, plays an important role in a number of cellular processes, but had not previously been associated with sensory hair cell specification. Reinforcing the crucial role of mutant lines, Steve Brown and colleagues and Saima Riazuddin and colleagues report in two papers published in the same issue of DMM that mice with a mutation in the Map3k1 gene experienced degeneration of their cochlear outer hair cells, leading to early-onset profound hearing loss. Collectively, their research shows that MAP3K1 is essential for the correct development and function of the mouse inner ear and hearing, and highlights the gene as a new candidate for studies into human sensorineural hearing.

Rare deafness syndromes

Deafness sometimes presents as an element of a well-characterised disease or rare and newly described congenital syndrome. As part of Deaf Awareness Week, it is worth reinforcing the importance of directing research resources to less common disorders, including those involving hearing loss. DMM has previously highlighted Siddiqi syndrome, a rare deafness–dystonia syndrome discovered in a family in northern Pakistan and first described in DMM by Saima Siddiqi, Hannie Kremer and colleagues. Waardenburg syndrome is another rare genetic disorder, characterised by varying degrees of hearing loss, as well as minor defects in structures arising from the neural crest, and a combination of skin and hair depigmentation. A forward genetic screen approach applied by Nicolas Pilon and colleagues revealed an overlapping gene pair as candidate loci for initiating the development of Waardenburg syndrome.

These papers highlight the diverse range of underlying conditions behind deafness, and how current research is laying the foundations for future prevention of hearing loss. During Deaf Awareness Week, DMM are celebrating the scientists, charitable organisation and funding bodies who are making this research possible.

Article collection for Deaf Awareness Week 2017

An in vitro model of murine middle ear epithelium
Apoorva Mulay, Khondoker M. Akram, Debbie Williams, Hannah Armes, Catherine Russell, Derek Hood, Stuart Armstrong, James P. Stewart, Steve D. M. Brown, Lynne Bingle, Colin D. Bingle
Disease Models & Mechanisms 2016 9: 1405-1417; doi: 10.1242/dmm.026658

A new model for non-typeable Haemophilus influenzae middle ear infection in the Junbo mutant mouse
Derek Hood, Richard Moxon, Tom Purnell, Caroline Richter, Debbie Williams, Ali Azar, Michael Crompton, Sara Wells, Martin Fray, Steve D. M. Brown, Michael T. Cheeseman
Disease Models & Mechanisms 2016 9: 69-79; doi: 10.1242/dmm.021659

Mouse genetics for studying mechanisms of deafness and more: an interview with Karen Steel
Disease Models & Mechanisms 2011 4: 716-718; doi: 10.1242/dmm.008813

The goya mouse mutant reveals distinct newly identified roles for MAP3K1 in the development and survival of cochlear sensory hair cells
Andrew Parker, Sally H. Cross, Ian J. Jackson, Rachel Hardisty-Hughes, Susan Morse, George Nicholson, Emma Coghill, Michael R. Bowl, Steve D. M. Brown
Disease Models & Mechanisms 2015 8: 1555-1568; doi: 10.1242/dmm.023176

MAP3K1 function is essential for cytoarchitecture of the mouse organ of Corti and survival of auditory hair cells
Rizwan Yousaf, Qinghang Meng, Robert B. Hufnagel, Ying Xia, Chandrakala Puligilla, Zubair M. Ahmed, Saima Riazuddin
Disease Models & Mechanisms 2015 8: 1543-1553; doi: 10.1242/dmm.023077

A homozygous FITM2 mutation causes a deafness–dystonia syndrome with motor regression and signs of ichthyosis and sensory neuropathy
Celia Zazo Seco, Anna Castells-Nobau, Seol-hee Joo, Margit Schraders, Jia Nee Foo, Monique van der Voet, S. Sendhil Velan, Bonnie Nijhof, Jaap Oostrik, Erik de Vrieze et al.
Disease Models & Mechanisms 2017 10: 105-118; doi: 10.1242/dmm.026476

Upregulation of the Nr2f1-A830082K12Rik gene pair in murine neural crest cells results in a complex phenotype reminiscent of Waardenburg syndrome type 4
Karl-F. Bergeron, Chloé M. A. Nguyen, Tatiana Cardinal, Baptiste Charrier, David W. Silversides, Nicolas Pilon
Disease Models & Mechanisms 2016 9: 1283-1293; doi: 10.1242/dmm.026773

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