The zebrafish as a psychiatric and neurodevelopmental tool
Understanding the causes of psychiatric and neurodevelopmental disorders is one of the greatest clinical challenges. Complex behavioral phenotypes and multigenic contributions make a broad range of approaches essential for defining molecular phenotypes and new treatments. We established the zebrafish as an useful system for analysis of autism spectrum and other psychiatric disorders. Part of this was developing the notion of an animal ‘tool’ that can address disease, even without recapitulating all human symptoms. This nomenclature has been useful for many investigators. My group has focused on the schizophrenia risk gene DISC1 and on the 16p11.2 CNV that is tightly associated with autism spectrum disorders, schizophrenia and other phenotypes. We demonstrated that DISC1 regulates the Wnt-PCP pathway. Further studies demonstrated that zebrafish kif22 and aldoa genes are dosage sensors for the 16p11.2 CNV. The work makes a unique contribution to the psychiatric research field, and studies are ongoing. I served as P.I. on all aspects of these studies.
- Sive, H. ‘Model’ or ‘tool’? New definitions for translational research. Dis. Model. Mech. 4, 137-138, 2011. PMCID: PMC
- DeRienzo, G., Bishop, J. A., Mao, Y., Pan, L., Ma, T.P., Moens, C.B., Tsai, L.H. and Sive, H. Disc1 regulates both b-catenin-mediated and non-canonical Wnt signaling during vertebrate embryogenesis. FASEB J. 25, 4184-4197, 2011. PMCID: PMC3236629.
- Blaker-Lee, A.,* Gupta, S.,* McCammon, J.,* De Rienzo, G. and Sive, H. Zebrafish homologs of 16p11.2, a genomic region associated with brain disorders, are active during brain development, and include two deletion dosage sensor genes. *Equal first authors. Model. Mech. 5, 834-851, 2012. PMCID: PMC3484866.
- McCammon, J.M. and Sive, H. Challenges in understanding psychiatric disorders and developing therapeutics: A role for zebrafish. Dis. Model Mech. 8(7):647-656, 2015. PMCID: PMC4486859.
The brain ventricular system
Formation of how the vertebrate neural tube formed, as precursor to the central nervous system was widely studied. However, few were asking why the tube formed. Since it takes the embryo huge effort to make a neural tube, we set about asking why is there a neural tube? My group pioneered the zebrafish as a useful and accessible model for study of brain ventricle development and function. We developed techniques to label, drain and refill the ventricles. We identified multiple mutants that impact zebrafish brain ventricle formation. Among the corresponding genes is the NaK-ATPase that is essential for both neuroepithelial formation and CSF production. We developed a drainage assay that showed necessity for CSF in brain cell survival, and is part of the answer to the question ‘why is there a neural tube?’. Using mass spectrometry and CSF complementation assays, we identified Retinol Binding Protein 4 (RBP4) as acting from the CSF through retinoic acid signaling to promote neuroepithelial cell survival. I served as P.I. on all aspects of these studies.
- Lowery, L.A. and Sive, H. Initial formation of zebrafish brain ventricles occurs independently of circulation and requires the nagie oko and snakehead/atp1a1a.1 gene products. Development, 132, 2057-2067, 2005.
- Chang, J.T., Lowery. L.A., and Sive, H. Multiple roles for the Na,K-ATPase subunits, Atp1a1 and Fxyd1, during brain ventricle development. Dev. Biol. 368(2), 312-322, 2012. PMCID: PMC3402628.
- Chang, J.T., Lehtinen, M.K. and Sive, H. Zebrafish cerebrospinal fluid mediates cell survival through a retinoid signaling pathway. Dev. Neurobiol., 76(1):75-92, 2016. Epub 2015 June 8. PMCID: PMC4644717.
- Fame, R.M., Chang, J.T., Hong, A., Aponte-Santiago, N.A. and Sive, H. Directional cerebrospinal fluid movement between brain ventricles in larval zebrafish. Fluids Barriers CNS 13(1): 11, 2016. PMCID: PMC4915066.
Earliest molecular steps in vertebrate neural patterning
Classical embryological analyses suggested that neural determination and patterning occurred during gastrulation, however no molecular data existed on whether any pattern existed in the embryo or arose during manipulations. We used subtractive cloning to isolate regulatory genes whose expression demonstrated that the nervous system is induced and has an anteroposterior axis by early gastrula in both Xenopus and zebrafish. Our work was among the first to identify retinoic acid as a neural (and mesodermal) posteriorizing factor. The work introduced molecular correlates and important regulators of neural patterning. I collaboratively developed a simple and popular subtractive cloning technique. We developed the first zebrafish explant system that set the standard for the field. Additionally, we were first to use in the embryo a dexamethasone-inducible gene expression system that has been useful across many model systems. I served as P.I. on all aspects of these studies.
- Sive, H., Draper,B., Harland, R. and Weintraub,H. Identification of a retinoic acid-sensitive period during primary axis formation in Xenopus laevis. Genes Dev. 4, 932-942, 1990.
- Kuo, J., Patel, M., Gamse, J., Merzdorf, C., Liu, X. Apekin, V. and Sive, H. opl: a zinc finger protein that regulates neural determination and patterning in Xenopus. Development 125, 2867-2882, 1998.
- Grinblat, J., Gamse, J., Patel, M. and Sive, H. Determination of the zebrafish forebrain: induction and patterning. Development 125, 4403-4416, 1998.
- Wiellette, E.L. and Sive, H. vhnf1 and FGF signals synergize to specify rhombomere identity in the zebrafish hindbrain. Development 130, 3821-3829, 2003.
The Extreme Anterior Domain
Classical embryologists had noted an anterior region where ectoderm and endoderm are directly juxtaposed, without intervening mesoderm that is present in all deuterostomes. However the significance of this region was unknown. I named the anterior, mesoderm-free region the ‘Extreme Anterior Domain’ (EAD). I decided to use the Xenopus cement gland as a positional marker for this region, and my group identified the molecular signals that position this organ. We went on to define the mouth as an EAD derivative, and the processes/genes involved in mouth formation. Subsequently, we identified the EAD as a facial organizer, which guides neural crest into the developing face.
We built this field. Our work established the cement gland as a useful positional marker. We re-opened classical investigations into mouth formation and defined novel molecular mechanisms, as well as a novel facial transplant technique. The notion that the EAD is an organizer was unanticipated, and this activity is likely to be conserved in mammals. I served as P.I. on all aspects of these studies.
- Sive, H., Hattori, K. and Weintraub, H. Progressive determination during formation of the anteroposterior axis in Xenopus laevis. Cell 58, 171-180, 1989.
- Dickinson, A. and Sive, H. The Wnt antagonists, Frzb-1 and Crescent locally regulate basement membrane dissolution in the developing primary mouth. Development 136, 1071-81, 2009. PMCID: PMC2685928.
- Jacox, L.*, Sindelka, R.*, Chen, J., Rothman, A., Dickinson, A. and Sive, H. The extreme anterior domain is an essential craniofacial organizer acting through Kinin-Kallikrein signaling. Cell Rep. 8, 596-609, 2014. PMCID: PMC4135435. * equal contribution.
- Jacox, L., Chen, J., Rothman, A., Lathrop-Marshall, H. and Sive, H. Formation of a ‘pre-mouth array’ from the extreme anterior domain is directed by neural crest and Wnt/PCP signaling. Cell Rep. 16(5):1445-55, 2016. PMCID: PMC4972695.