Citation: Chen Y, Yang X, Jing N (2023) Gain-of-function mutations in Trim71 linked to congenital hydrocephalus. PLoS Biol 21(2): e3001993. https://doi.org/10.1371/journal.pbio.3001993
Published: February 9, 2023
Copyright: © 2023 Chen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported in part by the National Key Basic Research and Development Program of China, 2019YFA0801402 and 2018YFA0800100 to XY, 2018YFA0107200, 2018YFA0801402, 2018YFA0108000, and 2017YFA0102700 to NJ, National Natural Science Foundation of China, 31900454 to XY, 31630043, 31900573 and 31871456 to NJ, and the Strategic Priority Research Program of the Chinese Academy of Sciences, XDA16020501 and XDA16020404 to NJ. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Hydrocephalus, one of the most severe and multifactorial neurological disorders, is classically defined as an active distension of the ventricular system, resulting from inadequate passage of cerebrospinal fluid (CSF) from its point of production in the choroid plexus to its sites of absorption into the systemic circulation . It is estimated to affect one in 1,000 infants and accounts for about 3% of all pediatric hospital charges . Impaired CSF flow, reabsorption, and/or excessive CSF production are classically thought to be the major causes for hydrocephalus. Clinically, patients affected with hydrocephalus are routinely treated with neurosurgical CSF shunting, but neurodevelopmental outcomes are poor and recurrence or morbidity remain common . The lack of effective medical strategies for treating hydrocephalus highlights the importance of a deep understanding of the pathology.
Recent findings from whole-exome sequencing (WES) of patients with congenital hydrocephalus (CH) revealed that genetic mutations contributed to more than 20% of sporadic CH cases . The frequent occurrence of mutations in genes encoding neurogenesis regulators indicates that an aberrant neurodevelopment process may be the pathological cause of human idiopathic CH. However, genetic studies also revealed that heterogeneous mutations could occur in a single CH-related gene. Thus, whether diverse genetic mutations (approximately 100 apparently heterogeneous CH risk genes) could converge to produce a unified molecular mechanism remains largely unexplored. For example, TRIM71, which encodes the RNA-binding protein tripartite motif containing 71 (also known as LIN-41), has recently been identified as a CH-causing gene in humans with evidence of pathological mutations at multiple sites [4,5].
Previous mechanistic studies had shown that mouse embryos with genetic knockout of Trim71 displayed a failure in neural tube closure and a lethal phenotype at around embryonic day (E) 9.5, and highlighted the importance of Trim71 in cortical neurogenesis . A mouse model harboring a CH-associated mutation in Trim71 (R595H, homolog of human R608H-TRIM71) showed ventriculomegaly with increased intracranial volume, which phenocopied pathological features of patients with CH . Interestingly, the differences in phenotypes between Trim71-KO mice and those with the CH-associated mutation raised the possibility of heterogeneous pathological mechanisms in CH.
In their new study, Liu and colleagues  took advantage of CRISPR-based genome editing and a mouse embryonic stem cell in vitro differentiation system to investigate the effect of 2 different CH-associated mutations (R595H-Trim71 and R783H-Trim71) during the neural differentiation process (Fig 1). Generally, they found that the 2 CH-associated mutations produced similar defects during neural differentiation. This result was in line with published findings using mouse embryos (Trim71-KO and a CH-associated mutant) that highlighted the important role of Trim71 in neurogenesis [6,7,9]. Surprisingly, by using crosslinking immunoprecipitation and sequencing (CLIP-seq), Liu and colleagues  provided evidence that these 2 different mutant Trim71 proteins bind to distinct repertoires of target mRNAs via gain-of-function mechanisms. In particular, R595H-Trim71 ectopically binds to Ctnnb1 transcripts, encoding β-catenin, and thus represses their normal translation. Deficiency in neural differentiation of R595H-Trim71 cells could be alleviated through modulating Wnt–β-catenin signaling. This finding raises the possibility that dysregulation of Wnt–β-catenin signaling is responsible for the differentiation defects in R595H-Trim71 mutant cells and for the pathology of patients with CH who carry the R608H-TRIM71 mutation (homolog of mouse R595H-Trim71). However, the pathogenic mechanism of the other mutation in Trim71 (R783H-Trim71) needs further investigation.
Mutations discovered in Trim71 (R595H and R783H) are located in the NHL domain. Mutant forms of Trim71 ectopically bind to distinct repertoires of target mRNAs. The ectopic binding to Ctnnb1 transcripts repressed translation and production of β-catenin. Dysregulation of Wnt–β-catenin signaling may affect stem cell neural differentiation, which could potentially cause congenital hydrocephalus. CC, coiled coil; RF, ring finger; WT, wild-type.
It is worth mentioning that some of the findings in the study by Liu and colleagues seem to differ slightly from those in prior studies. Liu and colleagues’ findings support gain-of-function mechanisms for CH associated with Trim71 mutations. By contrast, ventriculomegaly and CH-like phenotypes were observed in roughly one-fourth of neuroprogenitor-specific Trim71-KO mice in another study . The low penetrance argues against a unified molecular mechanism of CH. These discrepancies probably indicate that the point mutation in Trim71 (R595H) causes a gain-of-function that affects the Wnt–β-catenin pathway and induces CH, whereas the Trim71-KO caused CH through a different mechanism. There is an interesting parallel with a neurodevelopmental disorder caused by a point mutation in NR2F1. This mutation (R112K) in NR2F1 resulted in a potential gain-of-function pathology due a decrease in the binding activity of NR2F1, which affected the normal function of the Hedgehog pathway . These findings point to the intricacy of developmental neurological disorders and to the heterogeneity of their pathological mechanisms, which warrants further investigation. In particular, to clarify the discrepancies (gain-of-function versus loss-of-function) between the different model systems (point mutations versus knockout), further systematic comparison between mutations in Trim71 (R595H and R783H) and the Trim71-KO are required. Furthermore, whether mechanisms discovered in vitro can be extended to mouse neurogenesis or even to the pathogenesis of human CH remains an open question. Further research using more relevant models, such as animal models or human iPSCs carrying CH-associated mutations would be greatly beneficial to address these issues.
Overall, the study by Liu and colleagues  offers a novel perspective on the pathophysiology of CH, which involves a crosstalk between CH-associated genes and developmental signaling pathways. However, diverse types of pathogenesis may underly various point mutations, and aberrant regulation of developmental signaling pathways may only account for a small subset of patients with CH who carry particular mutations (within the 20% of mutation-caused CH cases). The full range of pathological mechanisms resulting from CH-associated mutations still remains to be uncovered. Novel insights from fundamental studies obtained with advanced technologies will broaden our understanding of CH and other neurodevelopmental disorders and may provide new personalized therapeutics to help patients.
- 1. Rekate H. The definition and classification of hydrocephalus: a personal recommendation to stimulate debate. Cerebrospinal Fluid Res. 2008;22(5):2. pmid:18211712
- 2. Simon TD, Riva-Cambrin J, Srivastava R, Bratton SL, Dean JM, Kestle JRW, et al. Hospital care for children with hydrocephalus in the United States: utilization, charges, comorbidities, and deaths. J Neurosurg Pediatr. 2008;1:131–137. pmid:18352782
- 3. Zhang J, Williams MA, Rigamonti D. Genetics of human hydrocephalus. J Neurol. 2006;253:1255–1266. pmid:16773266
- 4. Jin SC, Dong W, Kundishora AJ, Panchagnula S, Moreno-De-Luca A, Furey CG, et al. Exome sequencing implicates genetic disruption of prenatal neuro-gliogenesis in sporadic congenital hydrocephalus. Nat Med. 2020;26:1754–1765. pmid:33077954
- 5. Furey CG, Choi J, Jin SC, Zeng X, Timberlake AT, Nelson-Williams C, et al. De novo mutation in genes regulating neural stem cell fate in human congenital hydrocephalus. Neuron. 2018;99:302–314.e4. pmid:29983323
- 6. Cuevas E, Rybak-Wolf A, Rohde AM, Nguyen DTT, Wulczyn FG. Lin41/Trim71 is essential for mouse development and specifically expressed in postnatal ependymal cells of the brain. Front Cell Dev Biol. 2015;3:20. pmid:25883935
- 7. Duy PQ, Weise SC, Marini C, Li X-J, Liang D, Dahl PJ, et al. Impaired neurogenesis alters brain biomechanics in a neuroprogenitor-based genetic subtype of congenital hydrocephalus. Nat Neurosci. 2022;25:458–473. pmid:35379995
- 8. Liu Q, Novak MK, Pepin RM, Maschhoff KR, Hu W. Different congenital-hydrocephalus-associated mutations in Trim71 impair stem cell differentiation via distinct gain-of-function mechanisms. PLoS Biol. 2023; 21(2):e3001947.
- 9. Duy PQ, Furey CG, Kahle KT. Trim71/lin-41 links an ancient miRNA pathway to human congenital hydrocephalus. Trends Mol Med. 2019;25:467–469. pmid:30975633
- 10. Zhang K, Yu F, Zhu J, Han S, Chen J, Wu X, et al. Imbalance of excitatory/inhibitory neuron differentiation in neurodevelopmental disorders with an NR2F1 point mutation. Cell Rep. 2020;31:107521. pmid:32320667