Prenatal diagnosis of Hartsfield syndrome with a novel genetic variant.

A G2P0, 24-year-old woman presented at 17 weeks 3 days gestation for a fetal anatomy scan. Ultrasound identified bilateral upper and lower extremity ectrodactyly, semilobar holoprosencephaly, midface hypoplasia, and cleft lip and palate. Amniocentesis for a chromosome microarray demonstrated no significant copy number changes. Whole exome sequencing was subsequently completed, which revealed a de novo, likely pathogenic variant in FGFR1, c.2044G>A (D682N), consistent with FGFR1-related Hartsfield syndrome. This case highlights the first presumed molecularly confirmed prenatal diagnosis of Hartsfield syndrome and identifies a new pathogenic variant.

Holoprosencephaly in Patau Syndrome.

OBJECTIVE: To evaluate radiological (gestational and perinatal) and neonatal signs of patients with Patau syndrome and semilobar holoprosencephaly, as well as to report the association of both pathologies. CASE DESCRIPTION: This case report is about a female infant, born at term with trisomy of the chromosome 13 and semilobar holoprosencephaly, with thalamic fusion and a single cerebral ventricle, in addition to several other changes that worsened the patient's prognosis. COMMENTS: Chromosome 13 trisomy is a genetic alteration that leads to the symptoms that determines Patau syndrome. In this syndrome, cardiovascular, urogenital, central nervous system, facial structure and intellectual impairment are common, in addition to problems in limb formation, such as decreased humerus and femur length, polydactyly, hypotelorism and low ear implantation. It is estimated, however, that holoprosencephaly is present in only 24 to 45% of the patients with trisomy 13.

Fetal Description of the Pancreatic Agenesis and Holoprosencephaly Syndrome Associated to a Specific CNOT1 Variant.

Holoprosencephaly (HPE) is a clinically and genetically heterogeneous disease, which can be associated with various prenatal comorbidities not always detectable on prenatal ultrasound. We report on the case of a foetus carrying a semi-lobar HPE diagnosed at ultrasound, for which a fetal autopsy and a whole exome sequencing were performed following a medical termination of pregnancy. Neuropathological examination confirmed the semi-lobar HPE and general autopsy disclosed a total pancreas agenesis. Whole exome sequencing found the CNOT1 missense c.1603C>T, p.(Arg535Cys), occurring de novo in the foetus. The same variant was previously reported in 5 unrelated children. All individuals had HPE, and 4 out of 5 presented endo- and exocrine pancreatic insufficiency or total pancreas agenesis. CNOT1 encodes a subunit of the CCRN4-NOT complex, expressed at the early stage of embryonic development. This report is the first fetal description of the phenotype associating HPE and pancreatic agenesis linked to the recurrent CNOT1 missense c.1603C>T, p.(Arg535Cys). This finding strengthens the hypothesis of a specific recurrent variant associated with a particular phenotype of HPE and pancreas agenesis. The fetal autopsy that revealed the pancreas agenesis was crucial in guiding the genetic diagnosis and enabling accurate genetic counselling.

Alobar holoprosencephaly: Exploring mothers' perspectives on prenatal decision-making and prognostication.

OBJECTIVES: Parents receiving a prenatal diagnosis of alobar holoprosencephaly (HPE) often experience uncertainty regarding the pregnancy prognosis. There is little known about how best to counsel and support families receiving the diagnosis. This study explored parental experiences and wishes after receiving a prenatal diagnosis of alobar HPE. METHODS: This was a retrospective qualitative study. Semi-structured interviews were conducted to determine factors impacting parents' decision-making process, experiences with healthcare providers, and expectations for their child's length and quality of life. Interviews were analyzed using qualitative content analysis. RESULTS: Eight mothers who received a prenatal diagnosis of alobar HPE between 2013 and 2019 participated in the study. Parental expectations were based on information conveyed during prenatal counseling. Religious and personal beliefs, perceived suffering, and provider prognostication contributed to parent decisions and goals of care. Participants reported pressure to terminate the pregnancy. Parents were not prepared for the possibility of survival beyond the perinatal period. Most parents reported no regret in their choices. CONCLUSION: Patients receiving a prenatal diagnosis of alobar HPE desire access to balanced prenatal counseling about prognosis, morbidity, and mortality. Providers should explore values and beliefs that contribute to parents' goals of care and offer appropriate information and referrals.

Rapid diagnosis of trisomy 18 of maternal origin by quantitative fluorescent polymerase chain reaction analysis following tissue culture failure for conventional cytogenetic analysis in a fetus with holoprosencephaly, ventricular septal defect, arthrogryposis of bilateral wrists and aplasia of the thumbs.

OBJECTIVE: We present rapid diagnosis of trisomy 18 of maternal origin by quantitative fluorescent polymerase chain reaction (QF-PCR) analysis following tissue culture failure for conventional cytogenetic analysis in a fetus with holoprosencephaly (HPE), ventricular septal defect (VSD), arthrogryposis of bilateral wrists and aplasia of the thumbs. CASE REPORT: A 22-year-old, primigravid woman was referred for first-trimester ultrasound screening at 13 weeks of gestation, and the fetus was found to have HPE and VSD. The pregnancy was subsequently terminated at 14 weeks of gestation, and a malformed fetus was delivered with cebocephaly, arthrogryposis of bilateral wrists and aplasia of the thumbs. The umbilical cord and placental tissues were collected for genetic analysis. However, tissue culture failure for conventional cytogenetic analysis occurred because of contamination. QF-PCR analysis using the polymorphic DNA markers of D18S1369 (18q12.2) and D18S1361 (18q22.3) confirmed trisomy 18 of maternal origin. CONCLUSION: QF-PCR analysis is useful for rapid confirmation of trisomy 18 and the parental origin when tissue culture failure for conventional cytogenetic analysis occurs in pregnancy suspicious of fetal trisomy 18.

Compound heterozygous splicing CDON variants result in isolated ocular coloboma.

Ocular coloboma is caused by failure of optic fissure closure during development and recognized as part of the microphthalmia, anophthalmia, and coloboma (MAC) spectrum. While many genes are known to cause colobomatous microphthalmia, relatively few have been reported in coloboma with normal eye size. Genetic analysis including trio exome sequencing and Sanger sequencing was undertaken in a family with two siblings affected with bilateral coloboma of the iris, retina, and choroid. Pathogenic variants in MAC genes were excluded. Trio analysis identified compound heterozygous donor splice site variants in CDON, a cell-surface receptor known to function in the Sonic Hedgehog pathway, c.928 + 1G > A and c.2650 + 1G > T, in both affected individuals. Heterozygous missense and truncating CDON variants are associated with dominant holoprosencephaly (HPE) with incomplete penetrance and Cdon-/- mice display variable HPE and coloboma. A homozygous nonsense allele of uncertain significance was recently identified in a consanguineous patient with coloboma and a second molecular diagnosis. We report the first compound heterozygous variants in CDON as a cause of isolated coloboma. CDON is the first HPE gene identified to cause recessive coloboma. Given the phenotypic overlap, further examination of HPE genes in coloboma is indicated.

Nasal fistula, epidermal cyst and hypernatremia in a girl presenting holoprosencephaly due to a rare ZIC2 point mutation.

Holoprosencephaly is the most common brain malformation in humans and it is a complex genetic disorder. We report on a patient with holoprosencephaly caused by a rare ZIC2 mutation presenting a bifid nose associated with a nasal fistula and an epidermal cyst, besides hypernatremia. The patient was a 1 year and 4 months old girl that developed an important neuropsychomotor delay. Currently, she uses a wheelchair to move around and only emits sounds. Computed tomography (CT) scan revealed a semilobar holoprosencephaly and a Dandy-Walker variant. Head magnetic resonance imaging also disclosed corpus callosum agenesis and prefrontal subarachnoid space enlargement. On physical examination at 1 year and 4 months of age, we verified growth retardation, microcephaly, bilateral epicantic fold, upslanting palpebral fissures, bifid nose, and limbs spasticity secondary to hypertonia. Later, she began to present hypernatremia; however, its precise cause was not identified. At 6 years and 10 months of age, a nasal fistula was suspected. Facial CT scan showed an epidermal cyst at cartilaginous portion of the nasal septum. High resolution GTG-Banding karyotype was normal. However, molecular analysis through direct sequencing technique showed a mutation at regulatory region of the ZIC2 gene: c.1599*954T > A, a genetic variation previously described only in a Brazilian patient. Our patient presented findings still not reported in literature among patients with holoprosencephaly, including those with ZIC2 mutations. Thus, the spectrum of abnormalities associated to ZIC2 mutations may be broader and include other defects as those observed in our patient.

Holoprosencephaly in Kabuki syndrome.

Kabuki syndrome is a rare, multi-systemic disorder of chromatin regulation due to mutations in either KMT2D or KDM6A that encode a H3K4 methyltransferase and an H3K27 demethylase, respectively. The associated clinical phenotype is a direct result of temporal and spatial changes in gene expression in various tissues including the brain. Although mild to moderate intellectual disability is frequently recognized in individuals with Kabuki syndrome, the identification of brain anomalies, mostly involving the hippocampus and related structures remains an exception. Recently, the first two cases with alobar holoprosencephaly and mutations in KMT2D have been reported in the medical literature. We identified a de novo, pathogenic KMT2D variant (c.6295C > T; p.R2099X) using trio whole-exome sequencing in a 2-year-old female with lobar holoprosencephaly, microcephaly and cranio-facial features of Kabuki syndrome. This report expands the spectrum of brain anomalies associated with Kabuki syndrome underscoring the important role of histone modification for early brain development.

Novel synonymous and missense variants in FGFR1 causing Hartsfield syndrome.

Hartsfield syndrome is a rare clinical entity characterized by holoprosencephaly and ectrodactyly with the variable feature of cleft lip/palate. In addition to these symptoms patients with Hartsfield syndrome can show developmental delay of variable severity, isolated hypogonadotropic hypogonadism, central diabetes insipidus, vertebral anomalies, eye anomalies, and cardiac malformations. Pathogenic variants in FGFR1 have been described to cause phenotypically different FGFR1-related disorders such as Hartsfield syndrome, hypogonadotropic hypogonadism with or without anosmia, Jackson-Weiss syndrome, osteoglophonic dysplasia, Pfeiffer syndrome, and trigonocephaly Type 1. Here, we report three patients with Hartsfield syndrome from two unrelated families. Exome sequencing revealed two siblings harboring a novel de novo heterozygous synonymous variant c.1029G>A, p.Ala343Ala causing a cryptic splice donor site in exon 8 of FGFR1 likely due to gonadal mosaicism in one parent. The third case was a sporadic patient with a novel de novo heterozygous missense variant c.1868A>G, p.(Asp623Gly).

Cohesin complex-associated holoprosencephaly.

Marked by incomplete division of the embryonic forebrain, holoprosencephaly is one of the most common human developmental disorders. Despite decades of phenotype-driven research, 80-90% of aneuploidy-negative holoprosencephaly individuals with a probable genetic aetiology do not have a genetic diagnosis. Here we report holoprosencephaly associated with variants in the two X-linked cohesin complex genes, STAG2 and SMC1A, with loss-of-function variants in 10 individuals and a missense variant in one. Additionally, we report four individuals with variants in the cohesin complex genes that are not X-linked, SMC3 and RAD21. Using whole mount in situ hybridization, we show that STAG2 and SMC1A are expressed in the prosencephalic neural folds during primary neurulation in the mouse, consistent with forebrain morphogenesis and holoprosencephaly pathogenesis. Finally, we found that shRNA knockdown of STAG2 and SMC1A causes aberrant expression of HPE-associated genes ZIC2, GLI2, SMAD3 and FGFR1 in human neural stem cells. These findings show the cohesin complex as an important regulator of median forebrain development and X-linked inheritance patterns in holoprosencephaly.

Novel heterozygous variants in KMT2D associated with holoprosencephaly.

Lysine methyltransferase 2D (KMT2D; OMIM 602113) encodes a histone methyltransferase involved in transcriptional regulation of the beta-globin and estrogen receptor as part of a large protein complex known as activating signal cointegrator-2-containing complex (ASCOM). Heterozygous germline mutations in the KMT2D gene are known to cause Kabuki syndrome (OMIM 147920), a developmental multisystem disorder. Neither holoprosencephaly nor other defects in human forebrain development have been previously associated with Kabuki syndrome. Here we report two patients diagnosed with alobar holoprosencephaly in their antenatal period with de novo monoallelic KMT2D variants identified by trio-based exome sequencing. The first patient was found to have a stop-gain variant c.12565G>T (p.Gly4189*), while the second patient had a missense variant c.5A>G (p.Asp2Gly). Phenotyping of each patient did not reveal any age-related feature of Kabuki syndrome. These two cases represent the first report on association between KMT2D and holoprosencephaly.

Holoprosencephaly, orofacial cleft, and frontonaso-orbital encephaloceles: Genetic evaluation of a possible new syndrome.

Here we report on a Brazilian child who presented semilobar holoprosencephaly, frontonasal encephaloceles and bilateral cleft lip and palate. Malformations also included agenesis of the corpus callosum, abnormal cortical gyres, dilation of the aqueduct, bilateral endolymphatic sac, bilateral cystic cocci-vestibular malformation, and a cribriform defect. The 3D TC craniofacial images showed abnormal frontonasal transition region, with a bone bifurcation, and partial agenesis of nasal bone. The trunk and upper and lower limbs were normal. To our knowledge, this rare association of holoprocensephaly with frontonaso-orbital encephaloceles without limb anomalies has never been reported before. Karyotype was normal. SNP-array showed no copy-number alterations but revealed 25% of regions of homozygosity (ROH) with normal copy number, indicating a high coefficient of inbreeding, which significantly increases the risk for an autosomal recessive disorder. Whole exome sequencing analysis did not reveal any pathogenic or likely pathogenic variants. We discuss the possible influence of two variants of uncertain significance found within the patient's ROHs. First, a missense p.(Gly394Ser) in PCSK9, a gene involved in the regulation of plasma low-density lipoprotein cholesterol. Second, an inframe duplication p.(Ala75_Ala81dup) in SP8, a zinc-finger transcription factor that regulates signaling centers during craniofacial development. Further studies and/or the identification of other patients with a similar phenotype will help elucidate the genetic etiology of this complex case.

Schilbach-Rott syndrome associated with 9q22.32q22.33 duplication, involving the PTCH1 gene.

Schilbach-Rott syndrome (SRS, OMIM%164220) is a disorder of unknown aetiology that is characterised by hypotelorism, epichantal folds, cleft palate, dysmorphic face, hypospadia in males and mild mental retardation in some patients. To date, 5 families and 17 patients have exhibited this phenotype, and recurrence in two of these families suggests an autosomal dominant inheritance. SRS overlaps with a mild form of holoprosencephaly (HPE), but array-CGH analysis and sequencing of some HPE-related genes (SEPT9, SHH and TWIST) did not reveal any variants in at least one family. Herein, we investigated by array-CGH analysis a 11-year-old female patient and her father, both exhibiting the typical SRS phenotype, disclosing in the daughter-father couple the same microduplication of chromosome 9q22.32q22.33 [arr[hg19]9q22.32(98,049,611_98,049,636)x3,9q22.33 (99,301,483_99,301,508)x3], involving eight genes, including PTCH1. The duplication segregated with the disease, since it was not found in the healthy paternal grandparents of the proband. The gain-of-function variants of the PTCH1 gene are responsible for a mild form of HPE. This is the first genetic variant found in SRS. This finding reinforces the hypothesis that SRS belongs to the HPE clinical spectrum and suggests to perform array-CGH in patients with SRS phenotype and, if negative, to consider a potential benefit from sequencing of HPE-related genes.

Rare association of cyclopia with craniospinal rachischisis.

Cyclopia is a severe form of holoprosencephaly which results in children being born with just one eye, absence of nose and presence of a proboscis above the median eye. Incidence of cyclopia is around 1.05 in 1, 00,000 births, including stillbirths. The association of anencephaly with spinal rachichisis varies from 17-50%. However, the existence of cyclopia with anencephaly and spinal rachischisis has been reported only in 9 cases till date. We report one more case of cyclopia with anencephaly and spinal rachischisis. Awareness of this spectrum of association with cyclopia, albeit rare, will help in early antenatal diagnosis by fetal ultrasonography. Public education and strict adherence to folic acid supplementation can prevent this unfortunate anomaly.

The solitary median maxillary central incisor (SMMCI) syndrome: Associations, prenatal diagnosis, and outcomes.

Solitary median maxillary central incisor (SMMCI) syndrome is a complex disorder consisting of multiple, developmental defects involving midline structures of the head, which includes the cranial bones, the maxilla, and its container dentition (specifically the central incisor tooth germ), together with other midline structures of the body. SMMCI may appear as an isolated trait or in association with other midline developmental anomalies. We describe the case of a patient with SMMCI. He presented with a solitary median maxillary incisor, short stature, corpus callosum anomalies and a microform of holoprosencephaly (HPE), diabetes insipidus, and neurodevelopmental delay. The diagnosis was performed postnatally based on clinical features, radiological imaging, and a comprehensive genetic study. SMMCI can be diagnosed during the prenatal or neonatal periods or during infancy. Evaluation of the superior maxillary bone is important for prenatal diagnosis. Direct evaluation through bidimensional ultrasound or the use of multiplanar ultrasound or tridimensional reconstruction should be performed in cases of brain or face malformations. Early diagnosis can contribute to improved prenatal assessment and postnatal management.

Congenital eye anomalies: More mosaic than thought?

The eye is a sensory organ that primarily captures light and provides the sense of sight, as well as delivering non-visual light information involving biological rhythms and neurophysiological activities to the brain. Since the early 1990s, rapid advances in molecular biology have enabled the identification of developmental genes, genes responsible for human congenital diseases, and relevant genes of mutant animals with various anomalies. In this review, we first look at the development of the eye, and we highlight seminal reports regarding archetypal gene defects underlying three developmental ocular disorders in humans: (1) holoprosencephaly (HPE), with cyclopia being exhibited in the most severe cases; (2) microphthalmia, anophthalmia, and coloboma (MAC) phenotypes; and (3) anterior segment dysgenesis (ASDG), known as Peters anomaly and its related disorders. The recently developed methods, such as next-generation sequencing and genome editing techniques, have aided the discovery of gene mutations in congenital eye diseases and gene functions in normal eye development. Finally, we discuss Pax6-genome edited mosaic eyes and propose that somatic mosaicism in developmental gene mutations should be considered a causal factor for variable phenotypes, sporadic cases, and de novo mutations in human developmental disorders.