Background Helios (encoded by IKZF2), a member of the Ikaros family of transcription factors, is a zinc finger protein involved in embryogenesis and immune function. Although predominantly recognised for its role in the development and function of T lymphocytes, particularly the CD4+ regulatory T cells (Tregs), the expression and function of Helios extends beyond the immune system. During embryogenesis, Helios is expressed in a wide range of tissues, making genetic variants that disrupt the function of Helios strong candidates for causing widespread immune-related and developmental abnormalities in humans.
Methods We performed detailed phenotypic, genomic and functional investigations on two unrelated individuals with a phenotype of immune dysregulation combined with syndromic features including craniofacial differences, sensorineural hearing loss and congenital abnormalities.
Results Genome sequencing revealed de novo heterozygous variants that alter the critical DNA-binding zinc fingers (ZFs) of Helios. Proband 1 had a tandem duplication of ZFs 2 and 3 in the DNA-binding domain of Helios (p.Gly136_Ser191dup) and Proband 2 had a missense variant impacting one of the key residues for specific base recognition and DNA interaction in ZF2 of Helios (p.Gly153Arg). Functional studies confirmed that both these variant proteins are expressed and that they interfere with the ability of the wild-type Helios protein to perform its canonical function—repressing IL2 transcription activity—in a dominant negative manner.
Conclusion This study is the first to describe dominant negative IKZF2 variants. These variants cause a novel genetic syndrome characterised by immunodysregulation, craniofacial anomalies, hearing impairment, athelia and developmental delay.
- Congenital, Hereditary, and Neonatal Diseases and Abnormalities
- Genetics, Medical
- Sequence Analysis, DNA
- Immune System Diseases
Data availability statement
All data relevant to the study are included in the article or uploaded as supplementary information.
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AM and MV-S are joint first authors.
SET and AL are joint senior authors.
Collaborators Members of the Undiagnosed Diseases Network (UDN): Maria T. Acosta, Margaret Adam, David R. Adams, Raquel L. Alvarez, Justin Alvey, Laura Amendola, Ashley Andrews, Euan A. Ashley, Carlos A. Bacino, Guney Bademci, Ashok Balasubramanyam, Dustin Baldridge, Jim Bale, Michael Bamshad, Deborah Barbouth, Pinar Bayrak-Toydemir, Anita Beck, Alan H. Beggs, Edward Behrens, Gill Bejerano, Hugo J. Bellen, Jimmy Bennett, Beverly Berg-Rood, Jonathan A. Bernstein, Gerard T. Berry, Anna Bican, Stephanie Bivona, Elizabeth Blue, John Bohnsack, Devon Bonner, Lorenzo Botto, Brenna Boyd, Lauren C. Briere, Elly Brokamp, Gabrielle Brown, Elizabeth A. Burke, Lindsay C. Burrage, Manish J. Butte, Peter Byers, William E. Byrd, John Carey, Olveen Carrasquillo, Thomas Cassini, Ta Chen Peter Chang, Sirisak Chanprasert, Hsiao-Tuan Chao, Gary D. Clark, Terra R. Coakley, Laurel A. Cobban, Joy D. Cogan, Matthew Coggins, F. Sessions Cole, Heather A. Colley, Cynthia M. Cooper, Heidi Cope, Rosario Corona, William J. Craigen, Andrew B. Crouse, Michael Cunningham, Precilla D’Souza, Hongzheng Dai, Surendra Dasari, Joie Davis, Jyoti G. Dayal, Esteban C. Dell'Angelica, Katrina Dipple, Daniel Doherty, Naghmeh Dorrani, Argenia L. Doss, Emilie D. Douine, Laura Duncan, Dawn Earl, David J. Eckstein, Lisa T. Emrick, Christine M. Eng, Marni Falk, Elizabeth L. Fieg, Paul G. Fisher, Brent L. Fogel, Irman Forghani, William A. Gahl, Ian Glass, Bernadette Gochuico, Page C. Goddard, Rena A. Godfrey, Katie Golden-Grant, Alana Grajewski, Don Hadley, Sihoun Hahn, Meghan C. Halley, Rizwan Hamid, Kelly Hassey, Nichole Hayes, Frances High, Anne Hing, Fuki M. Hisama, Ingrid A. Holm, Jason Hom, Martha Horike-Pyne, Alden Huang, Sarah Hutchison, Wendy Introne, Rosario Isasi, Kosuke Izumi, Fariha Jamal, Gail P. Jarvik, Jeffrey Jarvik, Suman Jayadev, Orpa Jean-Marie, Vaidehi Jobanputra, Lefkothea Karaviti, Jennifer Kennedy, Shamika Ketkar, Dana Kiley, Gonench Kilich, Shilpa N. Kobren, Isaac S. Kohane, Jennefer N. Kohler, Susan Korrick, Mary Kozuira, Deborah Krakow, Donna M. Krasnewich, Elijah Kravets, Seema R. Lalani, Byron Lam, Christina Lam, Brendan C. Lanpher, Ian R. Lanza, Kimberly LeBlanc, Brendan H. Lee, Roy Levitt, Richard A. Lewis, Pengfei Liu, Xue Zhong Liu, Nicola Longo, Sandra K. Loo, Joseph Loscalzo, Richard L. Maas, Ellen F. Macnamara, Calum A. MacRae, Valerie V. Maduro, Rachel Mahoney, May Christine V. Malicdan, Laura A. Mamounas, Teri A. Manolio, Rong Mao, Kenneth Maravilla, Ronit Marom, Gabor Marth, Beth A. Martin, Martin G. Martin, Julian A. Martínez-Agosto, Shruti Marwaha, Jacob McCauley, Allyn McConkie-Rosell, Alexa T. McCray, Elisabeth McGee, Heather Mefford, J. Lawrence Merritt, Matthew Might, Ghayda Mirzaa, Eva Morava, Paolo Moretti, John Mulvihill, Mariko Nakano-Okuno, Stanley F. Nelson, John H. Newman, Sarah K. Nicholas, Deborah Nickerson, Shirley Nieves-Rodriguez, Donna Novacic, Devin Oglesbee, James P. Orengo, Laura Pace, Stephen Pak, J. Carl Pallais, Christina G.S. Palmer, Jeanette C. Papp, Neil H. Parker, John A. Phillips III, Jennifer E. Posey, Lorraine Potocki, Barbara N. Pusey Swerdzewski, Aaron Quinlan, Deepak A. Rao, Anna Raper, Wendy Raskind, Genecee Renteria, Chloe M. Reuter, Lynette Rives, Amy K. Robertson, Lance H. Rodan, Jill A. Rosenfeld, Natalie Rosenwasser, Francis Rossignol, Maura Ruzhnikov, Ralph Sacco, Jacinda B. Sampson, Mario Saporta, Judy Schaechter, Timothy Schedl, Kelly Schoch, Daryl A. Scott, C. Ron Scott, Vandana Shashi, Jimann Shin, Edwin K. Silverman, Janet S. Sinsheimer, Kathy Sisco, Edward C. Smith, Kevin S. Smith, Emily Solem, Lilianna Solnica-Krezel, Ben Solomon, Rebecca C. Spillmann, Joan M. Stoler, Kathleen Sullivan, Jennifer A. Sullivan, Angela Sun, Shirley Sutton, David A. Sweetser, Virginia Sybert, Holly K. Tabor, Queenie K.-G. Tan, Amelia L. M. Tan, Mustafa Tekin, Fred Telischi, Willa Thorson, Cynthia J. Tifft, Camilo Toro, Alyssa A. Tran, Rachel A. Ungar, Tiina K. Urv, Adeline Vanderver, Matt Velinder, Dave Viskochil, Tiphanie P. Vogel, Colleen E. Wahl, Melissa Walker, Stephanie Wallace, Nicole M. Walley, Jennifer Wambach, Jijun Wan, Lee-kai Wang, Michael F. Wangler, Patricia A. Ward, Daniel Wegner, Monika Weisz Hubshman, Mark Wener, Tara Wenger, Monte Westerfield, Matthew T. Wheeler, Jordan Whitlock, Lynne A. Wolfe, Kim Worley, Changrui Xiao, Shinya Yamamoto, John Yang, Zhe Zhang, Stephan Zuchner.
Members of the Care4Rare-SOLVE Leadership: Kym Boycott (lead; University of Ottawa), Michael Brudno (co-lead, University of Toronto), Francois Bernier (co-lead, University of Calgary), Clara van Karnebeek (co-lead, University of British Columbia), David Dyment (CHEO Research Institute), Kristin Kernohan (NSO, Children’s Hospital of Eastern Ontario), Micheil Innes (University of Calgary), Ryan Lamont (University of Calgary), Jillian Parboosingh (University of Calgary), Deborah Marshall (University of Calgary), Christian Marshall (University of Toronto), Roberto Mendoza (University of Toronto), James Dowling (University of Toronto), Robin Hayeems (University of Toronto), Bartha Knoppers (McGill University), Anna Lehman (University of British Columbia), and Sara Mostafavi (University of British Columbia).
Contributors Responsibility for the overall content of this work: SET and AL.
Conceptualisation: SET, AL, MV-S and AM. Lab experiments: MV-S, GXY and SL. Data Curation and variant interpretation: AM. Investigation and analysis: AM and MV-S. Writing (Original Draft): MV-S and AM. Writing (review and editing): MV-S, AM, SET, AL, JAR, DAS, EH, MS, AS, SKN, CvK, KLDB, CLY, CMB, HL, SM and KCW. Visualisation: AM and MV-S. Supervision: AL and SET. Clinical data acquisition: MV-S, MW and AS. Description of patient phenotype: JAM, MSA, FKK, RR, CMB, KJH, SRL, SKN, DAS, EH, JH, CLY, LA, SET and AL. All authors read and approved the final manuscript and agreed to be responsible for the accuracy and integrity of this manuscript. UDN and C4R members contributed their multidisciplinary expertise, fostered collaboration, optimised patient recruitment.
Funding MV-S is funded by the Vanier Canada Graduate Scholarship (Vanier CGS) and the University of British Columbia Four Year Doctoral Fellowship (4YF). CMB holds a Health Professional-Investigator award from Michael Smith Health Research BC and is supported by the Providence Healthcare Research Institute Early Career Investigator award. ST holds a Translational Research Grant Award from the Jeffrey Modell Foundation, a Tier 1 Canada Research Chair in Pediatric Precision Health, and the Aubrey J. Tingle Professor of Pediatric Immunology. ST and CMB hold a Project Grant from the Canadian Institutes of Health Research (PJT 178054). Part of this work was funded by a joint award held by AL, CvK and SM from Genome Canada, Genome BC, and BC Children’s Hospital Research Institute (F17-04161). Additionally, research reported in this manuscript was supported by the NIH Common Fund, through the Office of Strategic Coordination/Office of the NIH Director under Award Number U01HG007709. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Competing interests The Department of Molecular and Human Genetics at Baylor College of Medicine receives revenue from clinical genetic testing completed at Baylor Genetics Laboratories.
Provenance and peer review Not commissioned; externally peer reviewed.
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