Deletion of the last two exons of FGF10 in a family with LADD syndrome and pulmonary acinar hypoplasia

Diminished TMEM100 Expression in a Newborn With Acinar Dysplasia and a Novel TBX4 Variant: A Case Report

Acinar dysplasia (AcDys) of the lung is a rare lethal developmental disorder in neonates characterized by severe respiratory failure and pulmonary arterial hypertension refractory to treatment. Recently, abnormalities of TBX4-FGF10-FGFR2-TMEM100 signaling regulating lung development have been reported in patients with AcDys due to heterozygous single-nucleotide variants or copy-number variant deletions involving TBX4, FGF10, or FGFR2. Here, we describe a female neonate who died at 4 hours of life due to severe respiratory distress related to AcDys diagnosed by postmortem histopathologic evaluation. Genomic analyses revealed a novel deleterious heterozygous missense variant c.728A>C (p.Asn243Thr) in TBX4 that arose de novo on paternal chromosome 17. We also identified 6 candidate hypomorphic rare variants in the TBX4 enhancer in trans to TBX4 coding variant. Gene expression analyses of proband's lung tissue showed a significant reduction of TMEM100 expression with near absence of TMEM100 within the endothelium of arteries and capillaries by immunohistochemistry. These results support the pathogenicity of the detected TBX4 variant and provide further evidence that disrupted signaling between TBX4 and TMEM100 may contribute to severe lung phenotypes in humans, including AcDys.

Variants in FGF10 cause early onset of severe childhood interstitial lung disease: A detailed description of four affected children

INTRODUCTION

Fibroblast growth factor 10 (FGF10) is a signaling molecule with a well-established role for lung branching morphogenesis. Rare heterozygous, deleterious variants in the FGF10 gene are known causes of the lacrimo-auriculo-dento-digital (LADD) syndrome and aplasia of lacrimal and salivary glands. Previous studies indicate that pathogenic variants in FGF10 can cause childhood Interstitial Lung Disease (chILD) due to severe diffuse developmental disorders of the lung, but detailed reports on clinical presentation and follow-up of affected children are lacking.

METHODS

We describe four children with postnatal onset of chILD and heterozygous variants in FGF10, each detected by exome or whole genome sequencing.

RESULTS

All children presented with postnatal respiratory failure. Two children died within the first 2 days of life, one patient died at age of 12 years due to right heart failure related to severe pulmonary hypertension (PH) and one patient is alive at age of 6 years, but still symptomatic. Histopathological analysis of lung biopsies from the two children with early postpartum demise revealed diffuse developmental disorder representing acinar dysplasia and interstitial fibrosis. Sequential biopsies of the child with survival until the age of 12 years revealed alveolar simplification and progressive interstitial fibrosis.

DISCUSSION

Our report extends the phenotype of FGF10-related disorders to early onset chILD with progressive interstitial lung fibrosis and PH. Therefore, FGF10-related disorder should be considered even without previously described syndromic stigmata in children with postnatal respiratory distress, not only when leading to death in the neonatal period but also in case of persistent respiratory complaints and PH.

[Developments in Research on Salivary Biomarkers in the Diagnosis of Systemic Diseases]

Saliva, an important biological fluid secreted by oral glands, serves multiple functions. It performs cleaning and protective functions for oral tissues, safeguarding against biological, mechanical and chemical stimuli, while allowing for the sensory perception of taste and temperature. It is also responsible for the preliminary digestion of food. These functions and properties of saliva are attributed to the presence of electrolytes, buffers, proteins, glycoproteins, and lipids in saliva. Recent studies have found that saliva contains biomarkers that are closely connected with the pathophysiological status of the human body, suggesting that saliva makes an ideal biological fluid for drug monitoring and biomarker screening. Therefore, salivary biomarkers can be used as an instrument for physical monitoring and localization of the occurrence of diseases, thereby accomplishing early diagnosis of diseases and assessment of the overall health status of patients. However, the actual application of salivary biomarkers in the diagnosis and treatment of systemic diseases is still not widely available, and the establishment of evaluation criteria and the exploration of its mechanism are not sufficiently investigated. Herein, we reviewed the latest research findings on applying the salivary biomarkers in the diagnosis of systemic diseases.

Phenotypic spectrum of FGF10-related disorders: a systematic review

FGF10, as an FGFR2b-specific ligand, plays a crucial role during cell proliferation, multi-organ development, and tissue injury repair. The developmental importance of FGF10 has been emphasized by the identification of FGF10 abnormalities in human congenital disorders affecting different organs and systems. Single-nucleotide variants in FGF10 or FGF10-involving copy-number variant deletions have been reported in families with lacrimo-auriculo-dento-digital syndrome, aplasia of the lacrimal and salivary glands, or lethal lung developmental disorders. Abnormalities involving FGF10 have also been implicated in cleft lip and palate, myopia, or congenital heart disease. However, the exact developmental role of FGF10 and large phenotypic heterogeneity associated with FGF10 disruption remain incompletely understood. Here, we review human and animal studies and summarize the data on FGF10 mechanism of action, expression, multi-organ function, as well as its variants and their usefulness for clinicians and researchers.