Biomedical subjects

P L Mills

Publications and source records attributed to P L Mills.

7 recordsLinked to original sources

PubMed2001

Incomplete penetrance with normal MRI in a woman with germline mutation of the DCX gene.

X-linked isolated lissencephaly sequence (ILS) and subcortical band heterotopia are allelic human disorders associated with mutations of the DCX gene in both familial and sporadic forms. The authors describe a large Sardinian family in which three brothers with ILS have a missense mutation of the DCX gene. Their mother, a nonmosaic carrier, has a normal phenotype and cranial MRI. Skewed X-inactivation in the lymphocytes was also ruled out. This is the first report of an asymptomatic carrier of a DCX mutation likely due to apparent nonpenetrance.

Adolescent↗

PubMed2001

Mutation analysis of the DCX gene and genotype/phenotype correlation in subcortical band heterotopia.

Subcortical band heterotopia (SBH) comprises part of a spectrum of phenotypes associated with classical lissencephaly (LIS). LIS and SBH are caused by alterations in at least two genes: LIS1 (PAFAH1B1) at 17p13.3 and DCX (doublecortin) at Xq22.3-q23. DCX mutations predominantly cause LIS in hemizygous males and SBH in heterozygous females, and we have evaluated several families with LIS male and SBH female siblings. In this study, we performed detailed DCX mutation analysis and genotype-phenotype correlation in a large cohort with typical SBH. We screened 26 sporadic SBH females and 11 LIS/SBH families for DCX mutations by direct sequencing. We found 29 mutations in 22 sporadic patients and 11 pedigrees, including five deletions, four nonsense mutations, 19 missense mutations and one splice donor site mutation. The DCX mutation prevalence was 84.6% (22 of 26) in sporadic SBH patients and 100% (11 of 11) in SBH pedigrees. Maternal germline mosaicism was found in one family. Significant differences in genotype were found in relation to band thickness and familial vs sporadic status.

Brain↗

PubMed2000

The location and type of mutation predict malformation severity in isolated lissencephaly caused by abnormalities within the LIS1 gene.

Lissencephaly is a cortical malformation secondary to impaired neuronal migration resulting in mental retardation, epilepsy and motor impairment. It shows a severity spectrum from agyria with a severely thickened cortex to posterior band heterotopia only. The LIS1 gene on 17p13.3 encodes a 45 kDa protein named PAFAH1B1 containing seven WD40 repeats. This protein is required for optimal neuronal migration by two proposed mechanisms: as a microtubule-associated protein and as one subunit of the enzyme platelet-activating factor acetylhydrolase. Approximately 65% of patients with isolated lissencephaly sequence (ILS) show intragenic mutations or deletions of the LIS1 gene. We analyzed 29 non-deletion ILS patients carrying a mutation of LIS1 and we report 15 novel mutations. Patients with missense mutations had a milder lissencephaly grade compared with those with mutations leading to a shortened or truncated protein (P = 0.022). Early truncation/deletion mutations in the putative microtubule-binding domain resulted in a more severe lissencephaly than later truncation/deletion mutations (P < 0.001). Our results suggest that the lissencephaly severity in ILS caused by LIS1 mutations may be predicted by the type and location of the mutation. Using a spectrum of ILS patients, we confirm the importance of specific WD40 repeats and a putative microtubule-binding domain for PAFAH1B1 function. We suggest that the small number of missense mutations identified may be due to underdiagnosis of milder phenotypes and hypothesize that the greater lissencephaly severity seen in Miller-Dieker syndrome may be secondary to the loss of another cortical development gene in the deletion of 17p13.3.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2000

X-linked malformations of cortical development.

Disorders of the development of the human cortex are recognized as significant causes of mental retardation, epilepsy, and congenital neurologic deficits. These malformations may be restricted to the brain or may be one component of a generalized malformation syndrome. Through the efforts of several groups, a large number of human cortical malformations have been identified and classified. Studies of informative families and sporadic patients with specific chromosomal rearrangements or deletions have demonstrated a genetic basis for many of these disorders. Subsequent work has facilitated a precise genetic diagnosis and provided insight into the molecular basis of some of these malformations. This review will discuss four cortical malformation syndromes, which are known or likely to have an X-linked inheritance pattern: bilateral periventricular nodular heterotopia, X-linked lissencephaly/subcortical band heterotopia, X-linked lissencephaly with abnormal genitalia, and X-linked bilateral perisylvian polymicrogyria.

Brain Diseases↗

PubMed1997

Urorectal septal defects in a female and her offspring.

We report on a patient with an ectopic urethra opening into a septate vagina which was distended with urine. The anus and rectum were normal but separated from the urogenital sinus by a thin septum. After surgical repair the patient did well with the exception of recurrent urinary tract infections. At 16 years, she delivered a healthy boy by Cesarean section but miscarried a subsequent pregnancy 3 years later. The 12-13 week female fetus lacked a urethra and had an atretic vagina and cloacal anomalies consistent with a urorectal septum developmental defect. This report provides evidence that cloacal anomalies resulting from the improper development of the urorectal septum may have a genetic cause. Furthermore, we support the proposition previously set forth by Allen and Husmann [J Urol 145:1034-1039, 1991] that such anomalies be referred to as urorectal septal defects rather than cloacal anomaly variants. This terminology accurately represents the developmental defect and clearly distinguishes them from cloacal exstrophies, which are due to the abnormal development of the cloacal membrane and the subumbilical ventral abdominal wall.

Abortion, Missed↗

PubMed1996

Transgenic mdx mice expressing dystrophin with a deletion in the actin-binding domain display a "mild Becker" phenotype.

The functional significance of the actin-binding domain of dystrophin, the protein lacking in patients with Duchenne muscular dystrophy, has remained elusive. Patients with deletions of this domain (domain I) typically express low levels of the truncated protein. Whether the moderate to severe phenotypes associated with such deletions result from loss of an essential function, or from reduced levels of a functional protein, is unclear. To address this question, we have generated transgenic mice that express wild-type levels of a dystrophin deleted for the majority of the actin-binding domain. The transgene derived protein lacks amino acids 45-273, removing 2 of 3 in vitro identified actin interacting sites and part of hinge 1. Examination of the effect of this deletion in mice lacking wild-type dystrophin (mdx) suggests that a functional domain I is not essential for prevention of a dystrophic phenotype. However, in contrast to deletions in the central rod domain and to full-length dystrophin, both of which are functional at only 20% of wild-type levels, proteins with a deletion in domain I must be expressed at high levels to prevent a severe dystrophy. These results are also in contrast to the severe dystrophy resulting from truncation of the COOH-terminal domain that links dystrophin to the extracellular matrix. The mild phenotype observed in mice with domain I-deletions indicates that an intact actin-binding domain is not essential, although it does contribute to an important function of dystrophin. These studies also suggest the link between dystrophin and the subsarcolemmal cytoskeleton involves more than a simple attachment of domain I to actin filaments.

Actinin↗

PubMed1994

Deletion analysis of the dystrophin-actin binding domain.

Three sequence motifs at the N-terminus of dystrophin have previously been proposed to be important for binding to actin. By analyzing a series of purified bacterial fusion proteins deleted for each of these sites we have demonstrated that none of the three are critical for dystrophin-actin interactions. Instead, our data suggest that sequences in the N-terminal 90 amino acids of dystrophin, excluding a conserved KTFT motif, contain the major site for interaction with actin.

Actins↗