Loss-of-function variants in FREM1 have been demonstrated in Manitoba oculotrichoanal syndrome (MOTA) and bifid nose, renal agenesis, and anorectal malformations (BNAR) syndrome, but the broader phenotypic spectrum of FREM1 variants remains incompletely characterized. In this study, we report compound heterozygous variants in a prenatal case of bilateral renal agenesis. Exome sequencing revealed biallelic FREM1 variants: c.5622G>A (p.Trp1874*) and c.3274+4A>G (p.Gly1030_Ile1091del). Minigene and bioinformatic analyses confirmed that the splice site variant induces aberrant splicing and alters transcriptional expression levels. This finding underscores the crucial role of non-canonical splice site variants in FREM1 in the pathogenesis of bilateral renal agenesis. FREM1 autosomal recessive disorders include Manitoba oculotrichoanal (MOTA) syndrome, bifid nose with or without anorectal and renal anomalies (BNAR) syndrome, and isolated congenital anomalies of kidney and urinary tract (CAKUT). MOTA syndrome is characterized by an aberrant hairline (unilateral or bilateral wedge-shaped extension of the anterior hairline from the temple region to the ipsilateral eye) and anomalies of the eyes (widely spaced eyes, anophthalmia/microphthalmia and/or cryptophthalmos, colobomas of the upper eyelid, and corneopalpebral synechiae), nose (bifid or broad nasal tip), abdominal wall (omphalocele or umbilical hernia), and anus (stenosis and/or anterior displacement of the anal opening). The manifestations and degree of severity vary even among affected members of the same family. Growth and psychomotor development are normal. BNAR syndrome is characterized by a bifid or wide nasal tip, anorectal anomalies, and kidney malformations (e.g., renal agenesis, renal dysplasia). Typically, the eye manifestations of MOTA syndrome are absent. FREM1-related CAKUT has been reported in two boys from Macedonia with isolated CAKUT who had the same homozygous FREM1 pathogenic variants. The diagnosis of a FREM1 autosomal recessive disorder is established in a proband with biallelic pathogenic variants in FREM1 identified by molecular genetic testing. Treatment of manifestations: Intensive ocular lubrication to avoid exposure keratopathy before surgery is performed; release of synechiae between the eyelid and cornea; surgical intervention and/or prostheses for anophthalmia/microphthalmia and cryptophthalmos if warranted; supportive care for those with visual impairment. Rhinoplasty for notched ala nasi or bifid nose. Dilation for anal stenosis. Surgical closure of omphalocele; surgical or conservative management of umbilical hernia. Supportive treatment to preserve kidney function and electrolyte balance; dialysis and transplant if indicated in individuals with kidney failure. Psychosocial support and care coordination as needed. Surveillance: Assess kidney function in those with kidney disease with frequency per nephrologist; social work and family support at each visit. Phenotypes caused by biallelic FREM1 pathogenic variants – including MOTA syndrome, BNAR syndrome, and FREM1-related CAKUT – are inherited in an autosomal recessive manner. If both parents are known to be heterozygous for a FREM1 pathogenic variant, each sib of an affected individual has at conception a 25% chance of being affected, a 50% chance of being a carrier, and a 25% chance of being unaffected and not a carrier. Once the FREM1 pathogenic variants have been identified in an affected family member, carrier testing for at-risk relatives and prenatal/preimplantation genetic testing are possible.

The receptor tyrosine kinase Kit is expressed in cells derived from the trunk neural crest (NC), such as melanocytes; however, its role in cranial NC cell development is not fully understood. We investigated the effects of the heterozygous loss of Kit in NC cells during embryonic development by mating Kit2lox/+ mice with Wnt1-Cre mice to produce Wnt1-Cre; Kit2lox/+ embryos. In addition, Wnt1-Cre mice were mated with Rosa26R-yellow fluorescent protein (YFP) mice to visualize the tissue regions expressing Cre recombinase. Histological studies of the craniofacial regions of these mice were performed using samples from embryonic day (E) 12.5 and postnatal day (P) 1. Cellular apoptosis and proliferation were both analyzed through the immunostaining of tissue sections collected on E13.5 and E14.5 using anti-cleaved caspase 3 (CC3) to detect apoptosis and anti-Ki67 to detect proliferation. Cells from YFP-positive tissue regions of the facial areas of Wnt1-Cre; Kit+/+; Rosa26R-YFP embryos and Wnt1-Cre; Kit2lox/+; Rosa26R-YFP embryos collected on E12.5 and E15.5 were cultured and evaluated for cell proliferation. Compared with control littermates, Wnt1-Cre; Kit2lox/+ embryos exhibited midline cleft lip and bifid nose deformities. Substantial early (P1) postnatal lethality was observed in Wnt1-Cre; Kit2lox/+ mice, with none surviving to 3 weeks of age. YFP-positive cells from the maxillary regions of Wnt1-Cre; Kit2lox/+; Rosa26R-YFP embryos exhibited defective cell growth and self-renewal in vitro. Conditional heterozygous loss of Kit in Wnt1-Cre; Kit2lox/+ embryos is associated with craniofacial dysplasia and exhibit defective NC development in vitro and in vivo.

Dog breeding promotes within-group homogeneity through conformation to strict breed standards, while simultaneously driving between-group heterogeneity. There are over 350 recognized dog breeds that provide the foundation for investigating the genetic basis of phenotypic diversity. Typically, breed standard phenotypes such as stature, pelage, and craniofacial structure are analyzed through genetic association studies. However, such analyses are limited to assayed phenotypes only, leaving difficult-to-measure phenotypic subtleties easily overlooked. We investigated coding variation from over 2000 dogs, leading to discoveries of variants related to craniofacial morphology and stature. Breed-enriched variants were prioritized according to gene constraint, which was calculated using a mutation model derived from trinucleotide substitution probabilities. Among the newly found variants is a splice-acceptor variant in PDGFRA associated with bifid nose, a characteristic trait of Çatalburun dogs, implicating the gene's role in midline closure. Two additional LCORL variants, both associated with canine body size are also discovered: a frameshift that causes a premature stop in large breeds (>25 kg) and an intronic substitution found in small breeds (<10 kg), thus highlighting the importance of allelic heterogeneity in selection for breed traits. Most variants prioritized in this analysis are not associated with genomic signatures for breed differentiation, as these regions are enriched for constrained genes intolerant to nonsynonymous variation. This indicates trait selection in dogs is likely a balancing act between preserving essential gene functions and maximizing regulatory variation to drive phenotypic extremes.

BackgroundTessier No. 0 cleft, characterized by a bifid nose, significantly impacts facial development, imposing significant psychological and financial burdens on patients. Correction lacks consensus due to varied presentations and limited documentation of surgical treatments, notably in adults.SolutionLoco-regional soft tissue flaps can address minor deformities, but establishing a robust skeletal framework is often crucial for permanent correction.InnovationThis article introduces a novel and effective approach through reconstructive septorhinoplasty for addressing this anomaly.

Bifid nose is a rare congenital malformation, and few cases have been reported due to its low incidence. Herein, we report a new surgical procedure to treat patients with excess dorsal nasal tissue and an underfilled tip. A total of 22 patients with bifid nose deformities underwent surgery at our institution between 2012 and 2022. They were characterized by a broad nasal dorsum and a missing or underdeveloped nasal tip. We designed an innovative island flap of nasal dorsum as a new surgical method for treating this bifid nose deformity. Nasal length, tip projection, and photographs of nose morphology were obtained before and after the surgery. Outcomes, complications, indications, and patient satisfaction were analyzed and interviewed. The follow-up time ranges from 6 to 33 months (8.7 ± 5.5 months). The deformity was successfully corrected with an improved nasal appearance. Nasal length increased from initially 4.2 ± 0.3 mm to 4.6 ± 0.3 mm. Tip projection reached 19.9 ± 4.0 mm, which was 15.7 ± 2.9 mm before surgery. No severe complications were observed except poor venous reflux within postoperative 72 hours in four cases. Six patients (27.3%) got moderate healing and acceptable scars, and 14 patients (63.6%) got good healing. Most patients were very satisfied with the outcome (93.9%). The newly designed nasal dorsum island flap is a safe and effective technical approach to correct nose deformity featured by broad nasal dorsum and a missing or underdeveloped nasal tip.