# The Role of SPECC1L cytoskeletal protein in craniofacial development and malformation

> **NIH NIH R01** · UNIVERSITY OF KANSAS MEDICAL CENTER · 2020 · $325,125

## Abstract

PROJECT SUMMARY
Orofacial clefts are among the most common birth defects in the U.S., occurring in 1/800 live-births. The
lifetime cost for medical treatment, educational services and lost productivity averages more than $100,000 per
affected person. While a number of contributory genes have been identified, there is a continued need to
understand the underlying pathogenetic mechanisms. We identified the first de novo mutations in a novel
cytoskeletal SPECC1L gene in patients with oblique facial clefts. Recent identification of SPECC1L mutations
in patients with syndromic and nonsyndromic cleft lip and palate suggests that insights into the cellular and
molecular mechanism of SPECC1L function will be directly relevant to both severe and common facial
malformations. Our data show that Specc1l is expressed in the neural folds at E8.5, including in pre-migratory
cranial neural crest cells (CNCCs). Later at E9.5, it is expressed in post-migratory CNCCs, and in the
branchial arches at E10.5. To study SPECC1L function, we have generated severe, hypomorphic and
conditional mouse alleles of Specc1l deficiency. The severe mouse allele is embryonic lethal at E9.5 with
defective neural tube (NT) closure and incomplete delamination of post-migratory CNCCs. The hypomorphic
allele shows incompletely penetrant perinatal exencephaly phenotype. Moderate mutants with one
hypomorphic and one severe allele show highly penetrant palate closure delay. In addition, SPECC1L-deficient
cells show altered adherens junctions (AJs) and reduced PI3K-AKT signaling, both in vitro in cultured cells and
in vivo in Specc1l mutant tissue. Modulation of cell-cell contacts is important not only for CNCC delamination
from the neuroectoderm, but also for “collective” migration of CNCCs to their defined destinations. The central
hypothesis of this project is that SPECC1L modulates cell adhesion and collective migration by regulating the
density of epithelial and mesenchymal cell-cell contacts through PI3K-AKT signaling. In Aim 1, we propose to
investigate the effect of Specc1l dosage on craniofacial development using our hypomorphic, severe, and
conditional mouse alleles. In Aim 2, we will investigate SPECC1L mediation of AJ stability and PI3K-AKT
signaling using small molecule modulators of PI3K-AKT pathway. We will also explore the mechanism
underlying SPECC1L mediation of AKT stability. In Aim 3, we will use live-imaging to quantitatively assess
changes in collective cell behavior. Analyses will be conducted in ex vivo cultured E8.5 neural plate explants,
with CNCCs marked with Wnt1-Cre or Sox10-Cre. Successful completion of these studies will establish novel
SPECC1L-based links between AJs, cell polarity and PI3K-AKT signaling during facial morphogenesis and
palate closure. Understanding the correlation between SPECC1L dosage or functional deficiency and
collective cell migration will provide targets for future therapeutic or preventative strategies against orofacial
clefting.

## Key facts

- **NIH application ID:** 9968228
- **Project number:** 5R01DE026172-05
- **Recipient organization:** UNIVERSITY OF KANSAS MEDICAL CENTER
- **Principal Investigator:** Irfan Saadi
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $325,125
- **Award type:** 5
- **Project period:** 2016-07-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9968228

## Citation

> US National Institutes of Health, RePORTER application 9968228, The Role of SPECC1L cytoskeletal protein in craniofacial development and malformation (5R01DE026172-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9968228. Licensed CC0.

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